JP2008306113A - Manufacturing method of group iii nitride semiconductor, manufacturing method of group iii nitride semiconductor light emitting element, group iii nitride semiconductor light emitting element and lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a group III nitride semiconductor and a method for manufacturing a group III nitride semiconductor light emitting element by which doping concentration of dopant elements in a crystal can be easily optimized and film formation is efficiently performed by using a sputtering method. <P>SOLUTION: In this method, a substrate 11 and a target containing Ga elements are arranged in a chamber, and the group III nitride semiconductor of single crystal to which a dopant has been added is formed on the substrate 11 by a reactive sputtering method. Dopant elements are arranged in a dopant vessel which is provided to the outside of the chamber and connected to the inside of the chamber. The dopant elements are vaporized in the dopant vessel and supplied into the chamber, to add the dopant to the group III nitride semiconductor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention is a light emitting diode (LED), a laser diode (LD), a electronic device, etc., suitably used, formula _{Al a Ga b In c N (} 0 ≦ a ≦ 1,0 ≦ b ≦ 1,0 ≦ In particular, a method for producing a group III nitride semiconductor for forming a group III nitride semiconductor layer to which a dopant is added, relating to a method for producing a group III nitride semiconductor represented by c ≦ 1, a + b + c = 1), The present invention relates to a group III nitride semiconductor light emitting device manufacturing method, a group III nitride semiconductor light emitting device, and a lamp.

  Group III nitride semiconductors have a direct transition type band gap of energy corresponding to the range from visible light to ultraviolet light, and are excellent in luminous efficiency. Therefore, light emitting diodes (LEDs) and laser diodes (LDs) It is commercialized as a semiconductor light emitting device such as, and is used in various applications. Even when used in an electronic device, the group III nitride semiconductor has a potential for obtaining superior characteristics as compared with the case of using a conventional group III-V compound semiconductor.

Such group III nitride semiconductors are generally manufactured by metal organic chemical vapor deposition (MOCVD) using trimethylgallium, trimethylaluminum and ammonia as raw materials. The MOCVD method is a method in which a vapor of a raw material is contained in a carrier gas and transported to the substrate surface, and the raw material is decomposed by reaction with a heated substrate to grow crystals.
Conventionally, group III nitride semiconductor single crystal wafers are not commercially available, and group III nitride semiconductors are generally obtained by growing crystals on single crystal wafers of different materials.

On the other hand, research for producing a group III nitride semiconductor crystal by sputtering has also been conducted. For example, a method of directly forming a GaN film on a sapphire substrate by a sputtering method for the purpose of stacking high-resistance GaN. It has been proposed (for example, Patent Document 1). In the case of forming a GaN film by using the sputtering method, there are advantages such as low cost of equipment and stabilization of the process.
In addition, a method of forming a GaN layer on a Si (100) plane and an Al ₂ O ₃ (0001) plane by high-frequency magnetron sputtering using N ₂ gas has been proposed (for example, non-patent literature). 1).

  Further, a method has been proposed in which a GaN layer is formed using an apparatus in which a cathode and a solid target face each other and a mesh is placed between the substrate and the target (for example, Non-Patent Document 2).

In addition, when a layer made of a crystal of a group III nitride compound semiconductor as described above is formed, a technique for adding a dopant element such as Si or Mg is required for the purpose of controlling conductivity. There is also a report example of the experimental results of doping into the GaN film using it (for example, Non-Patent Document 3). However, this Non-Patent Document 3 does not describe a specific doping method, and it is impossible for a third party to perform additional experiments.
JP 60-039819 A Yukiko Ushibuchi (Y. USHIKU) et al., “Proceedings of the 21st Century Union Symposium”, Vol. 2nd, p295 (2003), T. Kikuma et al., “Vacuum”, Vol. 66, P233 (2002) “The 66th Japan Society of Applied Physics” pamphlet, 7a-N-6 (Autumn 2005), p248

When forming a film of GaN doped with a dopant element using a conventional sputtering method as described in Patent Document 1 and Non-Patent Documents 1 to 3, it is difficult to finely adjust the doping concentration. There is a problem that.
For this reason, when forming a GaN crystal using a sputtering method, the group balance of the group III nitride semiconductor that can easily optimize the mixing balance between the Ga element-containing target and the dopant and has good characteristics There has been a demand for a method capable of forming a film on a substrate with high efficiency and stability.

The present invention has been made in view of the above problems, and the doping concentration of the dopant element in the crystal of the group III nitride semiconductor can be easily optimized, and the group III can be efficiently formed using a sputtering method. It is an object of the present invention to provide a method for manufacturing a nitride semiconductor and a method for manufacturing a group III nitride semiconductor light emitting device.
Furthermore, it aims at providing the group III nitride semiconductor light-emitting device and lamp which were obtained with said manufacturing method and were excellent in the light emission characteristic.

As a result of diligent investigations to solve the above problems, the inventors of the present invention, when forming a group III nitride semiconductor, by vaporizing the dopant element and supplying it into the chamber, The present inventors have found that a group III nitride semiconductor having a good crystallinity can be easily controlled on a substrate by mixing the dopant with the dopant easily and stably and highly efficiently.
That is, the present invention relates to the following.

[1] Manufacture of a group III nitride semiconductor in which a substrate and a target containing Ga element are arranged in a chamber, and a single crystal group III nitride semiconductor doped with a dopant is formed on the substrate by a reactive sputtering method. A method comprising: disposing a dopant element in a dopant container provided outside the chamber and communicating with the interior of the chamber; and vaporizing the dopant element in the dopant container and supplying the dopant element into the chamber A method for producing a group III nitride semiconductor, comprising adding the dopant to the group III nitride semiconductor.
[2] The group III nitride semiconductor production according to [1], wherein the dopant element disposed in the dopant container is heated to vaporize the dopant element and supply it to the chamber. Method.
[3] The flow rate control means is provided between the dopant container and the chamber to adjust the supply amount of the dopant element vaporized in the dopant container into the chamber [1] Or the manufacturing method of the group III nitride semiconductor as described in [2].

[4] The atmosphere in the chamber at the time of forming the group III nitride semiconductor is a gas atmosphere containing a nitrogen atom-containing gas in a range of 20 to 80% and the balance containing at least an inert gas. The method for producing a group III nitride semiconductor according to any one of [1] to [3], wherein:
[5] According to [4], the nitrogen atom-containing gas present in the gas atmosphere in the chamber is nitrogen gas (N ₂ ), and the inert gas is argon gas (Ar). The manufacturing method of the group III nitride semiconductor of description.
[6] The temperature according to any one of [1] to [5], wherein the temperature of the substrate when forming the group III nitride semiconductor is in the range of 600 ° C. to 1050 ° C. A method for producing a group nitride semiconductor.

[7] The method for producing a group III nitride semiconductor according to any one of [1] to [6], wherein the dopant element includes a donor impurity.
[8] The method for producing a group III nitride semiconductor according to [7], wherein the donor impurity is a silicon (Si) element.
[9] The ratio of the Ga element and the Si element in the atmospheric gas in the chamber when forming the group III nitride semiconductor is in the range of 1: 0.0001 to 1: 0.00001. The method for producing a group III nitride semiconductor according to [8], wherein

[10] The method for producing a group III nitride semiconductor according to any one of [1] to [6], wherein the dopant element includes an acceptor impurity.
[11] The method for producing a group III nitride semiconductor according to [10], wherein the acceptor impurity is a magnesium (Mg) element.
[12] The ratio of Ga element to Mg element in the atmospheric gas in the chamber when forming the group III nitride semiconductor is in the range of 1: 0.01 to 1: 0.0001. [11] The method for producing a group III nitride semiconductor according to [11].

[13] A semiconductor layer in which an n-type semiconductor layer made of a group III nitride semiconductor, a light emitting layer, and a p-type semiconductor layer are sequentially stacked, and at least part of the n-type semiconductor layer is a single layer doped with a donor impurity. A method for producing a group III nitride semiconductor light-emitting device comprising a crystalline group III nitride semiconductor, wherein at least part of the p-type semiconductor layer comprises a single crystal group III nitride semiconductor to which an acceptor impurity is added, A step of forming at least a part of the n-type semiconductor layer by the method for producing a group III nitride semiconductor according to any one of [7] to [9] and / or at least one of the p-type semiconductor layers; A group is formed by the method for producing a group III nitride semiconductor according to any one of the above [10] to [12]. Manufacturing method of optical element.
[14] A group III nitride semiconductor light-emitting device obtained by the production method according to [13].
[15] A lamp comprising the group III nitride semiconductor light-emitting device according to [14].

  According to the method for producing a group III nitride semiconductor of the present invention, when a single crystal group III nitride semiconductor to which a dopant is added is formed by reactive sputtering, the film is provided outside the chamber. Since the dopant element is disposed in a dopant container communicated with the gas, and the dopant element is vaporized in the dopant container and supplied into the chamber, thereby adding the dopant to the group III nitride semiconductor. It is possible to easily control the mixing balance between the target containing the dopant and the dopant. This makes it possible to easily control the dopant concentration of the group III nitride semiconductor to be formed, so that the conductivity is optimally controlled according to the target characteristics and the group III nitride semiconductor having good crystallinity can be obtained. It is possible to form a film on the substrate with high efficiency and stability.

  In addition, according to the method for manufacturing a group III nitride semiconductor light emitting device of the present invention, at least part of the p-type semiconductor layer and / or the n-type semiconductor layer is a single crystal to which a dopant is added by the above-described manufacturing method. Group III nitride semiconductor light-emitting device comprising a layer made of a group III nitride semiconductor with controlled conductivity and good crystallinity and having excellent light emission characteristics An element is obtained.

  FIG. 1 to FIG. 5 are appropriately described below for a group III nitride semiconductor manufacturing method, a group III nitride semiconductor light emitting device manufacturing method, a group III nitride semiconductor light emitting device, and a lamp according to an embodiment of the present invention. The description will be given with reference.

[Method for Producing Group III Nitride Semiconductor]
In the method for manufacturing a group III nitride semiconductor according to this embodiment, a substrate 11 (see FIGS. 1 to 3) and a target 47 (see FIG. 5) containing a Ga element are arranged in a chamber 41 (see FIG. 5). In this method, a single crystal group III nitride semiconductor doped with a dopant is formed on the substrate 11 by a reactive sputtering method. The dopant container is provided outside the chamber 41 and communicates with the inside of the chamber 41. In this method, the dopant element 51 is disposed in the chamber 50, and the dopant element 51 is vaporized in the dopant container 50 and supplied into the chamber 41, thereby adding the dopant to the group III nitride semiconductor.

<Semiconductor laminated structure>
FIG. 1 is a diagram for explaining an example of a method for producing a group III nitride semiconductor according to the present invention, and is a schematic cross-sectional view showing an example of a stacked semiconductor in which a group III nitride semiconductor is formed on a substrate. . In the laminated semiconductor 10 shown in FIG. 1, a buffer layer 12 made of a group III nitride compound is laminated on a substrate 11, and an n-type semiconductor layer 14, a light emitting layer 15, and a p-type semiconductor layer 16 are formed on the buffer layer 12. A semiconductor layer 20 is sequentially formed.
The p-type semiconductor layer 16 of the present embodiment is made of a single crystal group III nitride semiconductor to which an acceptor impurity is added, and is formed by the group III nitride semiconductor manufacturing method of the present invention, which will be described in detail later. .
Hereinafter, the laminated structure of the group III nitride semiconductor of this embodiment will be described in detail.

"substrate"
In the present embodiment, the material that can be used for the substrate 11 is not particularly limited as long as it is a substrate material on which a group III nitride semiconductor crystal is epitaxially grown on the surface, and various materials can be selected and used. For example, sapphire, SiC, silicon, zinc oxide, magnesium oxide, manganese oxide, zirconium oxide, manganese zinc iron oxide, magnesium aluminum oxide, zirconium boride, gallium oxide, indium oxide, lithium gallium oxide, lithium aluminum oxide, neodymium gallium oxide Lanthanum strontium oxide aluminum tantalum, strontium titanium oxide, titanium oxide, hafnium, tungsten, molybdenum and the like. Among these, it is preferable to use a material having a hexagonal crystal structure such as sapphire or SiC for the substrate because a group III nitride semiconductor having good crystallinity can be stacked.
In addition, as the size of the substrate, a substrate having a diameter of about 2 inches is usually used. However, in the group III nitride semiconductor of the present invention, a substrate having a diameter of 4 to 6 inches can be used.

  In addition, while forming a buffer layer without using ammonia, and forming a base layer constituting an n-type semiconductor layer described later by a method using ammonia, the substrate material is formed into ammonia at a high temperature. When an oxide substrate or a metal substrate that is known to cause chemical modification by contact is used, the buffer layer of this embodiment functions as a coating layer, so that chemical modification of the substrate is performed. It is effective in preventing. In general, since the sputtering method can keep the substrate temperature low, even when a substrate made of a material that decomposes at a high temperature is used, the substrate 11 is not damaged. These layers can be formed.

"Buffer layer"
In the laminated semiconductor 10 of this embodiment, a buffer layer 12 made of a group III nitride compound is formed on a substrate 11 by reacting a metal raw material and a gas containing a group V element by being activated by plasma. Has been. A film formed by a method using a plasma metal raw material as in this embodiment has an effect that alignment is easily obtained.

  The group III nitride compound crystal forming such a buffer layer has a hexagonal crystal structure, and can be formed into a single crystal film by controlling the film formation conditions. Further, the group III nitride compound crystal can be formed into a columnar crystal having a texture based on a hexagonal column by controlling the film forming conditions. Note that the columnar crystal described here is a crystal which is separated by forming a crystal grain boundary between adjacent crystal grains, and is itself a columnar shape as a longitudinal sectional shape.

  The buffer layer 12 preferably has a single crystal structure from the viewpoint of the buffer function. As described above, the crystal of the group III nitride compound has a hexagonal crystal and forms a structure based on a hexagonal column. The crystal of the group III nitride compound can be formed as a crystal grown in the in-plane direction by controlling conditions such as film formation. When the buffer layer 12 having such a single crystal structure is formed on the substrate 11, the buffer function of the buffer layer 12 effectively acts. Therefore, the group III nitride semiconductor layer formed thereon is A crystal film having good orientation and crystallinity is obtained.

The thickness of the buffer layer 12 is preferably in the range of 20 to 80 nm. By setting the film thickness of the buffer layer 12 in this range, it has good orientation and functions effectively as a coating layer when each layer made of a group III nitride semiconductor is formed on the buffer layer 12. The buffer layer 12 is obtained.
If the thickness of the buffer layer 12 is less than 20 nm, the above-described function as a coat layer may not be sufficient. Further, when the buffer layer 12 is formed with a film thickness exceeding 80 nm, the film forming process time becomes long despite the change in the function as the coat layer, and the productivity may be lowered.

It is preferable that the buffer layer 12 has a composition containing Al. As a material constituting the buffer layer 12, any material can be used as long as it is a group III nitride semiconductor represented by the general formula AlGaInN. Furthermore, as V group, it is good also as a structure containing As and P.
Further, when the buffer layer 12 has a composition containing Al, it is preferable to use GaAlN. In this case, the composition of Al is preferably set to 50% or more. The buffer layer 12 is more preferably made of AlN.

  Any material can be used for the buffer layer 12 as long as it has the same crystal structure as that of the group III nitride semiconductor. However, the length of the lattice constitutes the underlayer described later. A group close to a group III nitride semiconductor is preferable, and a group IIIa element nitride of the periodic table is particularly preferable.

"Semiconductor layer"
As shown in FIG. 1, the laminated semiconductor 10 of the present embodiment is made of a group III nitride semiconductor on a substrate 11 via the buffer layer 12 as described above, and includes an n-type semiconductor layer 14 and a light emitting layer 15. And the semiconductor layer 20 comprised from the p-type semiconductor layer 16 is laminated | stacked. Further, in the illustrated stacked semiconductor 10, the base layer 14 a provided in the n-type semiconductor layer 14 is stacked on the buffer layer 12.

The group III nitride semiconductor, for example, and by the general formula _{Al X Ga Y In Z N 1} -A M A (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ Z ≦ 1, X + Y + Z = 1. Symbol M represents a group V element different from nitrogen (N), and 0 ≦ A <1.) Many gallium nitride-based compound semiconductors are known. and the general formula _{Al X Ga Y in Z N 1} -a M a (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ Z ≦ 1 , including the gallium compound semiconductor, X + Y + Z = 1 . symbol M nitrogen A gallium nitride-based compound semiconductor represented by (V) represents another group V element and 0 ≦ A <1) can be used without any limitation.

  Gallium nitride compound semiconductors can contain other group III elements in addition to Al, Ga, and In, and contain elements such as Ge, Si, Mg, Ca, Zn, Be, P, and As as necessary. You can also Furthermore, it is not limited to the element added intentionally, but may include impurities that are inevitably included depending on the film forming conditions and the like, as well as trace impurities that are included in the raw materials and reaction tube materials.

"N-type semiconductor layer"
The n-type semiconductor layer 14 is usually laminated on the buffer layer 12, and is composed of a base layer 14a, an n-type contact layer 14b, and an n-type cladding layer 14c. The n-type contact layer can also serve as an underlayer and / or an n-type cladding layer, but the underlayer can also serve as an n-type contact layer and / or an n-type cladding layer. It is.

{Underlayer}
The underlayer 14a of this embodiment is made of a group III nitride semiconductor, and is deposited on the buffer layer 12 by a conventionally known MOCVD method.
The material of the underlayer 14a is not necessarily the same as that of the buffer layer 12 formed on the substrate 11, and a different material may be used, but an Al _y Ga _1-y N layer (0 ≦ y ≦ 1, preferably 0 ≦ y ≦ 0.5, more preferably 0 ≦ y ≦ 0.1).

  When forming each layer made of a group III nitride semiconductor on a substrate, for example, directly forming a group III nitride semiconductor single crystal by sputtering on the (0001) C surface of a substrate made of sapphire, This is difficult due to the difference in lattice constant between the substrate and the group III nitride semiconductor. Therefore, in the present invention, the base layer 14 a made of a single crystal group III nitride semiconductor is formed in advance on the buffer layer 12. Since a single crystal layer of a group III nitride semiconductor having good crystallinity can be easily formed on the single crystal base layer 14a by a sputtering method, a group III whose conductivity is controlled by adding a dopant is added. A nitride semiconductor is easily obtained.

As a material used for the underlayer 14a, a group III nitride compound containing Ga, that is, a GaN-based compound semiconductor is used, and in particular, AlGaN or GaN can be preferably used.
When the buffer layer 12 is formed as an aggregate of columnar crystals made of AlN, it is necessary to loop dislocations by migration so that the underlying layer 14a does not inherit the crystallinity of the buffer layer 12 as it is. Examples of such a material include the GaN-based compound semiconductor containing Ga, and AlGaN or GaN is particularly preferable.

  The film thickness of the underlayer 14a is preferably in the range of 0.1 to 8 μm from the viewpoint of obtaining an underlayer with good crystallinity, and in the range of 0.1 to 2 μm is required for film formation. It is more preferable in that the process time can be shortened and productivity is improved.

The underlayer 14a may be configured such that a donor impurity (n-type impurity) is doped in the range of 1 × 10 ¹⁷ to 1 × 10 ¹⁹ / cm ³ as necessary, but is undoped (<1 × 10 ¹⁷ / Cm ³ ), and undoped is preferable in that good crystallinity can be maintained.
In the case where the substrate 11 is conductive, electrodes can be formed above and below the light emitting element by doping the base layer 14a with a dopant to make it conductive. On the other hand, when an insulating material is used for the substrate 11, a chip structure is provided in which the positive electrode and the negative electrode are provided on the same surface of the light emitting element. It is preferable to improve the crystallinity. Although it does not specifically limit as an n-type impurity, For example, Si, Ge, Sn, etc. are mentioned, Preferably Si and Ge are mentioned.

{N-type contact layer}
The n-type contact layer 14b of the present embodiment is made of a group III nitride semiconductor, and is deposited on the base layer 14a by sputtering.
As the n-type contact layer 14b, an Al _X Ga _1-X N layer (0 ≦ x ≦ 1, preferably 0 ≦ x ≦ 0.5, and more preferably 0 ≦ x ≦ 0.1) as in the base layer 14a. It is preferable that it is comprised. Further, the n-type impurity is preferably doped, and the n-type impurity is contained at a concentration of 1 × 10 ¹⁷ to 1 × 10 ¹⁹ / cm ³ , preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ / cm ^3. In view of maintaining good ohmic contact with the negative electrode, suppressing crack generation, and maintaining good crystallinity. Although it does not specifically limit as an n-type impurity, For example, Si, Ge, Sn, etc. are mentioned, Preferably it is Si and Ge. The growth temperature is the same as that of the underlayer. Further, as described above, the n-type contact layer 14b can also be configured to serve also as a base layer.

  The gallium nitride-based compound semiconductor constituting the underlayer 14a and the n-type contact layer 14b preferably has the same composition, and the total film thickness thereof is 0.1 to 20 μm, preferably 0.5 to 15 μm, more preferably It is preferable to set in the range of 1 to 12 μm. When the film thickness is within this range, the crystallinity of the semiconductor is maintained well.

{N-type cladding layer}
It is preferable to provide an n-type cladding layer 14c between the above-described n-type contact layer 14b and the light emitting layer 15 whose details will be described later. By providing the n-type cladding layer 14c, it is possible to improve the deterioration of flatness generated on the outermost surface of the n-type contact layer 14b. The n-type cladding layer 14c can be formed of AlGaN, GaN, GaInN, or the like using a sputtering method or the like. Alternatively, a heterojunction of these structures or a superlattice structure in which a plurality of layers are stacked may be used. Needless to say, in the case of using GaInN, it is desirable to make it larger than the band gap of GaInN of the light emitting layer 15.

The film thickness of the n-type cladding layer 14c is not particularly limited, but is preferably in the range of 5 to 500 nm, more preferably in the range of 5 to 100 nm.
The n-type impurity doping concentration in the n-type cladding layer 14c is preferably in the range of 1 × 10 ¹⁷ to 1 × 10 ²⁰ / cm ³ , more preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ /. It is in the range of cm ³ . A doping concentration within this range is preferable in terms of maintaining good crystallinity and reducing the operating voltage of the light emitting element.

"P-type semiconductor layer"
The p-type semiconductor layer 16 is generally composed of a p-type cladding layer 16a and a p-type contact layer 16b, and is formed using a reactive sputtering method. Further, the p-type contact layer can also serve as the p-type cladding layer.

  The p-type semiconductor layer 16 of this embodiment is formed by adding an acceptor impurity as a dopant for controlling conductivity to be p-type. Although it does not specifically limit as an acceptor impurity, For example, it is preferable to use Mg, and it is also possible to use Be and Zn similarly.

{P-type cladding layer}
The p-type cladding layer 16a is not particularly limited as long as it has a composition larger than the band gap energy of the light-emitting layer 15 described later in detail, and can confine carriers in the light-emitting layer 15, but preferably Al _d Examples include Ga _1-d N (0 <d ≦ 0.4, preferably 0.1 ≦ d ≦ 0.3). When the p-type cladding layer 16a is made of such AlGaN, it is preferable in terms of confining carriers in the light emitting layer 15.
The thickness of the p-type cladding layer 16a is not particularly limited, but is preferably 1 to 400 nm, and more preferably 5 to 100 nm.

The p-type dope concentration obtained by adding an acceptor impurity to the p-type cladding layer 16a is preferably in the range of 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ , more preferably 1 × 10 ^19. ˜1 × 10 ²⁰ / cm ³ . When the p-type dope concentration is in the above range, a good p-type crystal can be obtained without reducing the crystallinity.

{P-type contact layer}
The p-type contact layer 16b includes at least Al _e Ga _1-e N (0 ≦ e <0.5, preferably 0 ≦ e ≦ 0.2, more preferably 0 ≦ e ≦ 0.1). This is a gallium nitride compound semiconductor layer. When the Al composition is in the above range, it is preferable in terms of maintaining good crystallinity and good ohmic contact with a p-ohmic electrode (see translucent electrode 17 described later).
Although the film thickness of the p-type contact layer 16b is not specifically limited, 10-500 nm is preferable, More preferably, it is 50-200 nm. When the film thickness is within this range, it is preferable in terms of light emission output.

Further, when the p-type dope concentration obtained by adding the acceptor impurity to the p-type contact layer 16b is in the range of 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ , good ohmic contact can be maintained, It is preferable in terms of prevention of generation of cracks and maintenance of good crystallinity, and more preferably in the range of 5 × 10 ^{19 to} 5 × 10 ²⁰ / cm ³ .

"Light emitting layer"
The light emitting layer 15 is a layer on which the p-type semiconductor layer 16 is stacked on the n-type semiconductor layer 14 and can be formed by using a conventionally known MOCVD method or the like. Further, as shown in FIG. 1, the light emitting layer 15 is formed by alternately and alternately stacking a barrier layer 15a made of a gallium nitride compound semiconductor and a well layer 15b made of a gallium nitride compound semiconductor containing indium. In the illustrated example, the barrier layers 15a are stacked in the order in which they are arranged on the n-type semiconductor layer 14 side and the p-type semiconductor layer 16 side.

As the barrier layer 15a, for example, a gallium nitride-based material such as Al _c Ga _1-c N (0 ≦ c <0.3) having a larger band gap energy than the well layer 15b made of a gallium nitride-based compound semiconductor containing indium. A compound semiconductor can be suitably used.
Furthermore, the well layer 15b can be formed using indium as the semiconductor gallium nitride-based compound containing, for _example, can be used _{Ga 1-s In s N (} 0 <s <0.4) GaN such as indium.

  Further, the film thickness of the entire light emitting layer 15 is not particularly limited. For example, the thickness of the light emitting layer 15 is preferably in the range of 1 to 500 nm, and more preferably around 100 nm. When the film thickness is in the above range, it contributes to an improvement in light emission output.

<Manufacturing method>
In the method of manufacturing a group III nitride semiconductor according to this embodiment, as described above, the substrate 11 and the target 47 containing the Ga element are arranged in the chamber 41, and the single crystal III in which the dopant is added to the substrate 11 is used. A group nitride semiconductor is formed by a reactive sputtering method. A dopant element 51 is provided in a dopant container 50 provided outside the chamber 41 and communicated with the inside of the chamber 41. In this method, the dopant is added to the group III nitride semiconductor by being vaporized in the dopant container 50 and supplied into the chamber 41.

  In the manufacturing method of this embodiment, when a group III nitride semiconductor crystal is epitaxially grown on the substrate 11 to form the laminated semiconductor 10 as shown in FIG. 1, the buffer layer 12 is formed on the substrate 11, The semiconductor layer 20 is formed. In the example shown in the present embodiment, the buffer layer 12 is formed by sputtering, and the underlying layer 14a of the n-type semiconductor layer 14 is formed thereon by MOCVD, and then the n-type contact layer 14b and n-type are formed. Each layer of the cladding layer 14c is formed by sputtering, the light emitting layer 15 thereon is formed by MOCVD, and each of the p-type cladding layer 16a and the p-type contact layer 16b constituting the p-type semiconductor layer 16 is sputtered. It is a method of forming by law.

  In the manufacturing method of the present embodiment, each of the n-type contact layer 14b and the n-type cladding layer 14c is formed from a group III nitride semiconductor doped with Si and having n-type characteristics, using the manufacturing method described above. To do. In the present embodiment, the p-type cladding layer 16a and the p-type contact layer 16b are formed from a group III nitride semiconductor doped with Mg and having p-type characteristics, using the manufacturing method described above.

"Sputtering apparatus, film forming method, and film forming conditions"
Hereinafter, a configuration of a sputtering apparatus and a film forming method used in the manufacturing method according to the present embodiment to form each layer of the n-type contact layer 14b, the n-type clad layer 14c, the p-type clad layer 16a, and the p-type contact layer 16b. The film forming conditions will be described in detail using the sputtering apparatus 40 illustrated in FIG.

"Configuration of sputtering equipment"
In the sputtering apparatus 40 illustrated in FIG. 5, a target 47 containing a Ga element is disposed on an electrode 43 in a chamber 41, and the dopant container provided outside the chamber 41 is disposed in the chamber 41. 50 are connected in communication via a connecting pipe 52, and a dopant element 51 is disposed in the dopant container 50.

The electrode 43 is connected to the matching box 46, and the heater plate 44 is attached with the substrate 11 and the matching box 45. Such matching boxes 46 and 45 are each connected to a power supply 48, and current is supplied to the electrode 43 via the matching box 46, and current is supplied to the heater plate 44 via the matching box 45. The As a result, power is applied to the target 47 and a bias is applied to the substrate 11.
The above-mentioned matching boxes 46 and 45 are provided for matching impedance between the inside of the sputtering apparatus 40 and the high-frequency power supply 48.

  The dopant container 50 contains a dopant element 51 therein. In the present embodiment, the dopant element 51 is heated and vaporized by a heater 53 provided in the vicinity of the dopant container 50. The dopant element vaporized in the dopant container 51 is supplied into the chamber 41 through the connection pipe 52. Further, in the sputtering apparatus 40 of the example shown in FIG. 5, a control valve (flow rate control means) 52 a is provided in the path of the connection pipe 52, and the dopant element vaporized by the control valve 52 a is introduced into the chamber 41. The supply amount can be adjusted.

The sputtering apparatus used in the manufacturing method of this embodiment is preferably an apparatus that performs a film forming process by an RF sputtering method. When a semiconductor layer made of a group III nitride semiconductor is formed by sputtering, generally a group III metal is used as a target, and a nitrogen atom-containing gas (nitrogen gas: N ₂ , ammonia: NH ₃ or the like) is placed in the chamber of the sputtering apparatus. Is used, and a reactive sputtering method (reactive reactive sputtering method) in which a group III metal and nitrogen are reacted in a gas phase is used. As sputtering methods, there are RF sputtering and DC sputtering. When reactive sputtering is used as in the manufacturing method of the present invention, DC sputtering with continuous discharge is intensely charged, and film formation speed is controlled. It becomes difficult. For this reason, in the manufacturing method of the present invention, it is preferable to use the RF sputtering method, and when using the DC sputtering method, use a sputtering apparatus employing a pulsed DC sputtering method capable of applying a bias in a pulsed manner. Is preferred.

  When RF sputtering is used, it is preferable to move the position of the magnet within the target as a method for avoiding charging. A specific motion method can be selected depending on a sputtering apparatus to be used, and can be swung or rotated. In the sputtering apparatus 40 illustrated in FIG. 5, a magnet 42 is provided below the target 47, and the magnet 42 is configured to be able to rotate under the target 47.

Further, when a semiconductor layer made of a group III nitride semiconductor is formed by sputtering, it is preferable to supply a higher energy reactive species to the substrate, so that the substrate 11 is positioned in the plasma in the sputtering apparatus 40. In addition, it is preferable to configure as a positional relationship in which the target 47 and the substrate 11 face each other. In addition, the distance between the substrate 11 and the target 47 is preferably in the range of 10 to 100 mm.
Moreover, since it is preferable that impurities are not left in the chamber 41 as much as possible, the ultimate vacuum of the sputtering apparatus 40 is preferably 1.0 × 10 ⁻³ Pa or less.

  In the illustrated sputtering apparatus 40, the heater 53 is used as a means for vaporizing the dopant element disposed in the dopant container 50. However, the present invention is not limited to this, and other vaporization means may be used. It is.

  Further, in the sputtering apparatus 40, the connection pipe 52 is provided with a control valve 52a so that the supply amount of the vaporized dopant element into the chamber 41 can be adjusted, but other control means may be used. It is also possible to omit such flow rate control means. In such a case, for example, a method of adjusting the temperature applied by the heater 53 to the dopant container 50 for vaporizing the dopant element can be employed. By adopting such a method, the internal pressure of the dopant container 50 is increased to be higher than the internal pressure of the chamber 41, so that steam is supplied toward the chamber and the supply amount is adjusted by the heating temperature. Is possible.

"Film formation method by vaporizing dopant element"
When the semiconductor layer is formed on the substrate 11 using the sputtering apparatus 40 as described above, first, for example, argon gas and nitrogen gas are supplied into the chamber 41 and provided in the heater plate 44. The heater plate 44 generates heat by a heating means (not shown), and the substrate 11 is heated to a predetermined temperature, that is, the growth temperature of each layer grown on the substrate 11.
Then, a current is supplied to the electrode 43 while the substrate 11 is heated, power is applied to the target 47, current is supplied to the heater plate 44, and a bias is applied to the substrate 11. At the same time, the dopant element 51 disposed in the dopant container 50 is heated by the heater 53. At this time, the control valve 52a is opened.

  By such an operation, the target 47 containing Ga element is exposed to the plasma of argon gas and nitrogen gas, and Ga particles are ejected from the target 47. At the same time, heating and vaporization are performed in the dopant container 50. The doped dopant element is supplied into the chamber 41 as particles in a vapor state. Then, each particle described above is supplied so as to hit the surface of the substrate 11 attached to the heater plate 44 or the film laminated on the substrate 11, so that the GaN doped with the dopant on the substrate 11. A layer made of (Group III nitride semiconductor) is formed.

  Here, in the manufacturing method of the present embodiment, the control valve 52a is opened and closed to change the supply amount of the vaporized dopant element particles into the chamber 41, whereby the Ga element in the atmospheric gas in the chamber 41 is changed. And the ratio of the dopant element can be controlled. At this time, the amount of Ga element and dopant element particles in the atmospheric gas in the chamber 41 matches the ratio of Ga element and dopant element in the GaN crystal to be formed. By appropriately adjusting the supply amount, the doping concentration in the GaN (semiconductor layer) crystal to be formed can be controlled to an optimum value.

`` Film formation conditions ''
In the manufacturing method of the present embodiment, the dopant element 51 is disposed in the dopant container 50 provided in the sputtering apparatus 40 as described above for doping of the group III nitride semiconductor with the dopant element (impurity), and the heater 53 This is performed by heating and vaporizing the gas and supplying the gas into the gas atmosphere in the chamber 41. At this time, as the dopant element disposed in the dopant container 50, donor impurities and acceptor impurities as described below can be appropriately used in accordance with the target characteristics of the group III nitride semiconductor to be formed.
Hereinafter, each film forming condition by the sputtering method will be described in detail.

(Donor impurity)
In the present embodiment, by vaporizing and using a dopant element made of a donor impurity, a layer made of a group III nitride semiconductor in which the donor impurity is added and the conductivity is controlled to be n-type can be formed.
As the donor impurity, it is preferable to use a silicon (Si) element. However, as described above, Ge, Sn, or the like can be used in addition to Si.

  Moreover, when forming a group III nitride semiconductor using Si element as a dopant element, the ratio of Ga element and Si element in the atmospheric gas in the chamber 41 is 1: 0.0001 to 1: 0.00001. It is preferable to be in the range. When the ratio of Ga element to Si element in the atmospheric gas is within the above range, the conductivity is optimally controlled to n-type, and a layer made of a group III nitride semiconductor with good crystallinity can be formed. .

  According to the manufacturing method of this embodiment, as described above, by using a donor impurity as a dopant element, for example, at least a part of the n-type semiconductor layer 14 in the stacked semiconductor 10 as illustrated in FIG. The film can be formed from an n-type GaN single crystal whose conductivity is controlled to n-type.

(Acceptor impurity)
In this embodiment, by vaporizing and using a dopant element made of an acceptor impurity, a layer made of a group III nitride semiconductor to which the acceptor impurity is added and the conductivity is controlled to be p-type can be formed.
As the acceptor impurity, it is preferable to use a magnesium (Mg) element. However, as described above, Be, Zn, or the like can be used in addition to Mg.

  When forming a group III nitride semiconductor using Mg element as a dopant element, the ratio of Ga element to Mg element in the atmospheric gas in the 41 chamber is 1: 0.01 to 1: 0.0001. It is preferable to be in the range. If the ratio of Ga element to Mg element in the atmospheric gas is within the above range, the conductivity is optimally controlled to p-type, and a layer made of a group III nitride semiconductor with good crystallinity can be formed. .

According to the manufacturing method of this embodiment, as described above, by using an acceptor impurity as a dopant element, for example, at least a part of the p-type semiconductor layer 16 in the stacked semiconductor 10 as illustrated in FIG. The film can be formed from a p-type GaN single crystal whose conductivity is controlled to be p-type and has a carrier concentration of 1 to 4 × 10 ¹⁶ atoms / cm ³ .

(Gas atmosphere in the chamber)
Other parameters that are important when forming a semiconductor layer made of a group III nitride semiconductor by sputtering include the partial pressure of the nitrogen atom-containing gas, the film formation rate, the substrate temperature, the bias, and the power.
First, the gas atmosphere in the chamber 41 of the sputtering apparatus 40 is an atmosphere containing a nitrogen atom-containing gas (nitrogen: N ₂ gas, NH ₃ gas, etc.). Such a nitrogen atom-containing gas is turned into plasma by sputtering and decomposed into nitrogen atoms to be a raw material for crystal growth. Further, in order to efficiently sputter the target 47, the atmosphere is further mixed with an inert gas having a large weight and low reactivity such as argon (Ar).
The proportion of the nitrogen atom-containing gas in the gas atmosphere in the chamber 41, for example, nitrogen gas flow rate ratio of the total flow rate of the nitrogen gas (N ₂₎ and argon (Ar) may be 20% to 98% . If the flow rate ratio of nitrogen gas is less than 20%, the sputtering raw material may adhere as metal, and if the flow rate ratio of nitrogen gas exceeds 98%, the amount of argon is too small and the sputtering rate decreases.

In order to stack a group III nitride semiconductor having particularly good crystallinity, the ratio of the nitrogen atom-containing gas in the atmosphere in the chamber 41 is set to a range of 20 to 80%, and the balance contains an inert gas. It must be gas.
Note that the gas containing an inert gas may contain hydrogen gas (H ₂ ) or the like in addition to an inert gas such as Ar.

(Deposition rate)
The deposition rate of the semiconductor layer made of a group III nitride semiconductor by sputtering is preferably 0.01 to 10 nm / second. If the deposition rate exceeds 10 nm / second, the stacked group III nitride semiconductor does not become crystalline but becomes amorphous, and if it is less than 0.01 nm / second, the process becomes uselessly long and is used for industrial production. It becomes difficult.

(Substrate temperature)
As a result of diligent experiments by the present inventors, it is generally preferable that the substrate temperature be in the range of 600 to 1200 ° C. in order to form a semiconductor layer made of a group III nitride semiconductor having good crystallinity by sputtering. Became clear. When the substrate temperature is lower than 600 ° C., migration of reactive species on the substrate surface is suppressed, and it becomes difficult to form a group III nitride semiconductor with good crystallinity. Further, when the substrate temperature exceeds 1200 ° C., the formed group III nitride semiconductor may be decomposed again.

  Further, in order to easily control the conductivity of the semiconductor layer by adding a dopant such as a donor impurity or an acceptor impurity, the substrate temperature needs to be in a range of 600 ° C. to 1050 ° C. By setting the substrate temperature in the range of 600 ° C. to 1050 ° C., a group III nitride semiconductor with low defect density such as point defects and good crystallinity can be grown. This makes it possible to easily control the conductivity by adding a dopant to the group III nitride semiconductor.

(Bias and power)
Further, in order to activate the migration of reactive species on the surface of the substrate 11 during crystal growth, it is preferable that the bias applied to the substrate 11 side and the power applied to the target 47 side are large. For example, the bias applied to the substrate 11 during film formation is preferably 1.5 W / cm ² or more, and the power applied to the target 47 during film formation is in the range of 1.5 W / cm ^{2 to 5} kW / cm ^2. Is preferred.

(Target composition)
The composition of the semiconductor layer made of a group III nitride semiconductor can be controlled by adjusting the composition of the group III metal used for the target to a desired value. For example, when forming a layer made of GaN, Ga metal may be used for the target, and when forming an AlGaN layer, an AlGa alloy may be used for the target. Further, when forming InGaN, an InGa alloy may be used. Since the composition of the group III nitride semiconductor varies depending on the composition of the group III metal of the target 47, a semiconductor layer made of a group III nitride semiconductor having a desired composition can be obtained by experimentally determining the composition of the target 47. It becomes possible to form.

  Alternatively, for example, when an AlGaN layer is stacked, both Ga metal and Al metal may be juxtaposed as targets. In this case, it is possible to control the composition of the laminated AlGaN layer by changing the ratio of the surface areas of the Ga metal target and the Al metal target. Similarly, when an InGaN layer is stacked, both a Ga metal target and an In metal target can be juxtaposed.

“Formation of laminated semiconductors”
A method for forming each layer when forming the laminated semiconductor 10 as shown in FIG. 1 using the manufacturing method of this embodiment will be described in detail below.

"Formation of buffer layer"
After introducing the substrate 11 into the reactor and before forming the buffer layer 12, it is desirable to perform pretreatment using a method such as sputtering. Specifically, the surface can be prepared by exposing the substrate 11 to Ar or N ₂ plasma. For example, by applying plasma such as Ar gas or N ₂ gas to the surface of the substrate 11, organic substances and oxides attached to the surface of the substrate 11 can be removed. In this case, if a voltage is applied between the substrate 11 and the chamber, the plasma particles efficiently act on the substrate 11. By applying such pretreatment to the substrate 11, the buffer layer 12 can be formed over the entire surface 11a of the substrate 11, and the crystallinity of the film formed thereon can be improved.
Further, when the buffer layer 12 is formed on the substrate 11, the substrate 11 may be subjected to wet pretreatment. For example, with respect to the substrate 11 made of silicon, a well-known RCA cleaning method or the like is performed and the surface is hydrogen-terminated to stabilize the film forming process.

  After pre-processing the surface of the substrate 11, argon and nitrogen gas are introduced into the sputtering apparatus, and the temperature of the substrate 11 is set to about 500 ° C. Then, a high frequency bias is applied to the substrate 11 side, power is applied to the Al target side made of metal Al, and a buffer layer 12 made of AlN is formed on the substrate 11 while keeping the pressure in the furnace constant. .

  Examples of a method for forming the buffer layer 12 on the substrate 11 include a sputtering method, a MOCVD method, a pulse laser deposition (PLD) method, a pulsed electron beam deposition (PED) method, and the like. However, since the sputtering method is the simplest and suitable for mass production, it is a suitable method. Note that when DC sputtering is used, the target surface may be charged up, and the deposition rate may not be stable. Therefore, it is desirable to use pulse DC sputtering or RF sputtering.

"Semiconductor layer formation"
On the buffer layer 12, the n-type semiconductor layer 14, the light emitting layer 15, and the p-type semiconductor layer 16 are stacked in this order to form a semiconductor layer 20 made of a group III nitride semiconductor. In the manufacturing method of the present embodiment, as described above, after the base layer 14a of the n-type semiconductor layer 14 is formed by the MOCVD method, each of the n-type contact layer 14b and the n-type cladding layer 14c is formed by the sputtering method, The light emitting layer 15 thereon is formed by MOCVD, and the p-type cladding layer 16a and the p-type contact layer 16b constituting the p-type semiconductor layer 16 are formed by sputtering.

In this embodiment, the growth method of the gallium nitride-based compound semiconductor when forming the semiconductor layer 20 is not particularly limited. In addition to the above-described sputtering method, MOCVD (metal organic chemical vapor deposition), HVPE (hydride vapor phase). All methods known to grow nitride semiconductors such as a growth method) and MBE (molecular beam epitaxy method) can be applied. Among these methods, in MOCVD, hydrogen (H ₂ ) or nitrogen (N ₂ ) is used as a carrier gas, trimethyl gallium (TMG) or triethyl gallium (TEG) is used as a Ga source which is a group III material, and trimethyl aluminum is used as an Al source. (TMA) or triethylaluminum (TEA), trimethylindium (TMI) or triethylindium (TEI) as the In source, ammonia (NH ₃ ), hydrazine (N ₂ H ₄ ) or the like as the N source which is a group V material. . In addition, as a dopant, for n-type, monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used as a Si raw material, germanium gas (GeH ₄ ) or tetramethyl germanium ((CH ₃ ) ₄ Ge) is used as a Ge raw material. Or an organic germanium compound such as tetraethylgermanium ((C ₂ H ₅ ) ₄ Ge) can be used. In the MBE method, elemental germanium can also be used as a doping source. For the p-type, for example, biscyclopentadienyl magnesium (Cp ₂ Mg) or bisethylcyclopentadienyl magnesium (EtCp ₂ Mg) is used as the Mg raw material.

  The gallium nitride-based compound semiconductor as described above can contain other group III elements in addition to Al, Ga, and In. If necessary, dopant elements such as Ge, Si, Mg, Ca, Zn, and Be can be added. Can be contained. Furthermore, it is not limited to the element added intentionally, but may include impurities that are inevitably included depending on the film forming conditions and the like, as well as trace impurities that are included in the raw materials and reaction tube materials.

(Formation of n-type semiconductor layer)
When forming the semiconductor layer 20 of the present embodiment, first, the base layer 14a of the n-type semiconductor layer 14 is deposited on the buffer layer 12 using a conventionally known MOCVD method. Next, the n-type contact layer 14b and the n-type cladding layer 14c are formed on the base layer 14a by the sputtering method by the manufacturing method of the present embodiment as described above. At this time, the n-type contact layer 14b and the n-type cladding layer 14c can be formed using the same sputtering apparatus.

As a method of forming the base layer 14a made of a single crystal group III nitride semiconductor on the substrate 11, the above-described Al _y Ga _1-y N (0 ≦ y) is used by using the MOCVD method as in this embodiment. There is a method in which a low-temperature buffer layer composed of ≦ 1) is formed on the substrate 11 and a single-crystal GaN layer is formed thereon by MOCVD at a temperature higher than the temperature at which the low-temperature buffer layer is formed.
Further, instead of forming the low-temperature buffer layer by using the MOCVD method, a polycrystalline buffer layer made of Al _y Ga _1-y N (0 ≦ y ≦ 1) is formed by using the sputtering method. Alternatively, a single crystal GaN layer may be formed by MOCVD. At this time, a single-crystal GaN layer may be grown by sputtering.

Here, when the underlayer is formed by a sputtering method, for example, the n-type contact layer 14b and the n-type formed by the sputtering method using the manufacturing method of the present embodiment as described above. The film forming process can be performed using the same chamber 41 as the clad layer 14c. In this case, the underlayer is formed undoped without supplying a dopant element made of donor impurities (Si) into the chamber 41. On the other hand, the n-type contact layer 14b and the n-type cladding layer 14c are formed by supplying a dopant element made of a donor impurity (Si) into the chamber 41, thereby adding the donor impurity and making the conductivity n-type. A controlled GaN layer is obtained.
Thus, in the case where the underlying layer is formed using the sputtering method in addition to the n-type contact layer 14b and the n-type cladding layer 14c, the manufacturing equipment for forming the n-type semiconductor layer 14 is used. Since the (sputtering apparatus) can be made common, productivity can be improved and manufacturing cost can be reduced.

(Formation of light emitting layer)
On the n-type cladding layer 14c, the light emitting layer 15 is formed by a conventionally known MOCVD method. The light emitting layer 15 formed in this embodiment as illustrated in FIG. 1 has a laminated structure starting with a GaN barrier layer and ending with the GaN barrier layer, and includes six barrier layers 15a made of Si-doped GaN, And five well layers 15b made of non-doped In _0.2 Ga _0.8 N are alternately stacked.

(Formation of p-type semiconductor layer)
A p-type semiconductor layer 16 composed of a p-type cladding layer 16a and a p-type contact layer 16b is formed on the light-emitting layer 15, that is, on the barrier layer 15a that is the uppermost layer of the light-emitting layer 15, as described above. A film is formed by sputtering using the manufacturing method.

In the present embodiment, first, a p-type clad layer 16a made of Al _0.1 Ga _0.9 N doped with Mg is formed on the light emitting layer 15 (the uppermost barrier layer 15a), and Mg is formed thereon. A p-type contact layer 16b made of doped Al _0.02 Ga _0.98 N is formed. At this time, the same sputtering apparatus can be used for stacking the p-type cladding layer 16a and the p-type contact layer 16b.
In the film forming process of the p-type semiconductor layer 16 including the p-type cladding layer 16a and the p-type contact layer 16b, the dopant element made of an acceptor impurity (Mg) is used in the chamber 41 by using the manufacturing method of the present embodiment described above. To form a GaN layer in which acceptor impurities are added and conductivity is controlled to be p-type.

According to the group III nitride semiconductor manufacturing method of the present embodiment as described above, when the single crystal group III nitride semiconductor to which the dopant is added is formed by reactive sputtering, the outside of the chamber 41 is formed. The dopant element 51 is disposed in a dopant container 50 that is provided in the chamber 41 and communicated with the interior of the chamber 41, and the dopant element 51 is vaporized in the dopant container 50 and supplied into the chamber 41. Since the dopant is added to the physical semiconductor, the mixing balance between the Ga element-containing target and the dopant can be easily controlled.
This makes it possible to easily control the dopant concentration of the group III nitride semiconductor to be formed, so that the conductivity is optimally controlled according to the target characteristics and the group III nitride semiconductor having good crystallinity can be obtained. It is possible to form a film on the substrate with high efficiency and stability.

Moreover, in the manufacturing method of this embodiment, the film-forming process of a group III nitride semiconductor can be made into the process of performing a film-forming process, changing a dopant density | concentration suitably by the said structure. In this case, for example, a process of forming a film while applying a dopant concentration gradient to the semiconductor layer, or a process of stacking the semiconductor layers while performing synchronous doping that changes the dopant concentration according to the target characteristics can be performed.
As a result, the group III nitride semiconductor can be formed with high efficiency while optimally controlling the conductivity, and the productivity can be improved and the manufacturing equipment such as the sputtering apparatus can be shared. Costs can be reduced.

  The group III nitride semiconductor according to the present invention, in which a dopant element is vaporized and added and the conductivity is optimally controlled, is provided in a light emitting element such as a light emitting diode (LED) or a laser disk (LD) which will be described in detail later. It can be used for various semiconductor elements such as p-type contact layers and electronic devices such as transistors.

[Method for Producing Group III Nitride Semiconductor Light-Emitting Device]
The method for manufacturing a group III nitride semiconductor light emitting device according to the present invention includes an n-type semiconductor layer 14, a light emitting layer 15 and a p-type semiconductor each made of a group III nitride semiconductor as illustrated in FIG. 3 (see also FIG. 1). When manufacturing a group III nitride semiconductor light emitting device (hereinafter sometimes abbreviated as a light emitting device) 1 including a semiconductor layer 20 in which layers 16 are sequentially stacked, the n-type semiconductor layer 14 and / or p This is a method including a step of forming at least a part of the type semiconductor layer 16 by the method of manufacturing a group III nitride semiconductor as described above.

<Laminated structure of light emitting element>
2 and 3 are views for explaining an example of the method for manufacturing the light emitting device of the present embodiment, in which a laminated semiconductor 10 in which each layer made of a group III nitride semiconductor is formed on a substrate (see FIG. 1). FIG. 2 is a schematic view illustrating an example in which the light-emitting element 1 is configured by using FIG. 2, FIG. 2 is a plan view, and FIG.
In the light emitting device 1 of the present embodiment, a translucent positive electrode 17 is laminated on a p-type semiconductor layer 16 of a laminated semiconductor 10 manufactured by the above manufacturing method, a positive electrode bonding pad 18 is formed thereon, and n The negative electrode 19 is roughly laminated on the exposed region 14d formed in the n-type contact layer 14b of the type semiconductor layer 14.
The n-type semiconductor layer 14 of the present embodiment is made of a single crystal group III nitride semiconductor to which a donor impurity is added, and the p-type semiconductor layer 16 is a single crystal group III to which an acceptor impurity is added. It is made of a nitride semiconductor and is formed by the manufacturing method of the present embodiment.

"Translucent positive electrode"
The translucent positive electrode 17 is a translucent electrode formed on the p-type semiconductor layer 16 (p-type contact layer 16b) of the laminated semiconductor 10 described above.
The material of the translucent positive electrode 17 is not particularly limited, but ITO (In ₂ O ₃ —SnO ₂ ), AZO (ZnO—Al ₂ O ₃ ), IZO (In ₂ O ₃ —ZnO), GZO (ZnO— Materials such as Ga ₂ O ₃ ) can be provided by conventional means well known in the art. In addition, any structure including a conventionally known structure can be used without any limitation.
The translucent positive electrode 17 may be formed so as to cover almost the entire surface of the p-type semiconductor layer 16 doped with Mg, or may be formed in a lattice shape or a tree shape with a gap.

"Positive electrode bonding pad and negative electrode"
The positive electrode bonding pad 18 is an electrode formed on the translucent positive electrode 17 described above.
As the material of the positive electrode bonding pad 18, various structures using Au, Al, Ni, Cu, and the like are well known, and these well-known materials and structures can be used without any limitation.
The thickness of the positive electrode bonding pad 18 is preferably in the range of 100 to 1000 nm. Further, in view of the characteristics of the bonding pad, the larger the thickness, the higher the bondability. Therefore, the thickness of the positive electrode bonding pad 18 is more preferably 300 nm or more. Furthermore, it is preferable to set it as 500 nm or less from a viewpoint of manufacturing cost.

The negative electrode 19 is formed to be in contact with the n-type contact layer 14 b of the n-type semiconductor layer 14 in the semiconductor layer in which the n-type semiconductor layer 14, the light emitting layer 15, and the p-type semiconductor layer 16 are sequentially stacked on the substrate 11. The
For this reason, when the negative electrode 19 is provided, an exposed region 14d of the n-type contact layer 14b is formed by removing a part of the p-type semiconductor layer 16, the light emitting layer 15 and the n-type semiconductor layer 14, and on this, A negative electrode 19 is formed.
As the material of the negative electrode 19, negative electrodes having various compositions and structures are well known, and these known negative electrodes can be used without any limitation, and can be provided by conventional means well known in this technical field.

<Method for manufacturing light-emitting element>
Below, an example of the manufacturing method of the light emitting element 1 as shown in FIG.2 and FIG.3 is demonstrated.
The manufacturing method of the light-emitting element 1 of the present embodiment uses the laminated semiconductor 10 obtained by the above-described manufacturing method, and a transparent positive electrode 17 is laminated on the p-type semiconductor layer 16 of the laminated semiconductor 10 and the positive electrode is formed thereon. In this method, the bonding pad 18 is formed, and the negative electrode 19 is laminated on the exposed region 14 d formed in the n-type contact layer 14 b of the n-type semiconductor layer 14.

"Formation of translucent positive electrode"
By the method as described above, the translucent positive electrode 17 made of ITO is formed on the substrate 11 on the p-type contact layer 16b of the laminated semiconductor 10 in which the buffer layer 12 and the semiconductor layer are laminated.
The method for forming the translucent positive electrode 17 is not particularly limited, and can be provided by conventional means well known in this technical field. In addition, any structure including a conventionally known structure can be used without any limitation.

Further, as described above, the material of the translucent positive electrode 17 is not limited to ITO, and can be formed using materials such as AZO, IZO, and GZO.
Further, after forming the translucent positive electrode 17, thermal annealing may be performed for the purpose of alloying or transparency, but it may not be performed.

"Formation of positive electrode bonding pad and negative electrode"
A positive electrode bonding pad 18 is further formed on the translucent positive electrode 17 formed on the laminated semiconductor 10.
The positive electrode bonding pad 18 can be formed, for example, by laminating Ti, Al, and Au materials in order from the surface side of the translucent positive electrode 17 by a conventionally known method.

  Further, when forming the negative electrode 19, first, a part of the light emitting layer 15, the p-type semiconductor layer 16, and the n-type semiconductor layer 14 formed on the substrate 11 is removed by a method such as dry etching. An exposed region 14d of the n-type contact layer 14b is formed (see FIGS. 2 and 3). Then, on the exposed region 14d, for example, each material of Ni, Al, Ti, and Au is laminated in order from the surface side of the exposed region 14d by a conventionally known method to form the negative electrode 19 having a four-layer structure. can do.

  Then, as described above, after the wafer having the translucent positive electrode 17, the positive electrode bonding pad 18 and the negative electrode 19 provided on the laminated semiconductor 10 is ground and polished, the back surface of the substrate 11 is made into a mirror-like surface. For example, a light emitting element chip (light emitting element 1) can be obtained by cutting into a 350 μm square.

  According to the method for manufacturing a group III nitride semiconductor light emitting device of this embodiment as described above, at least a part of the n-type semiconductor layer 14 and / or the p-type semiconductor layer 16 is the same as that of the present embodiment. According to the manufacturing method, it is a method of forming from a single crystal group III nitride semiconductor to which a dopant is added. Therefore, a layer made of a group III nitride semiconductor having good crystallinity with optimal conductivity controlled is provided. Thus, a group III nitride semiconductor light emitting device having excellent light emission characteristics can be obtained.

[lamp]
By combining the group III nitride semiconductor light emitting device according to the present invention and the phosphor as described above, a lamp can be configured by means well known to those skilled in the art. Conventionally, a technique for changing the emission color by combining a light emitting element and a phosphor is known, and such a technique can be adopted without any limitation.
For example, it is possible to obtain light having a longer wavelength than that of the light emitting element by appropriately selecting the phosphor, and white light emission by mixing the light emitting wavelength of the light emitting element itself with the wavelength converted by the phosphor. It can also be set as the lamp which exhibits.
Further, the lamp can be used for any purpose such as a general bullet type, a side view type for a portable backlight, and a top view type used for a display.

  For example, as in the example shown in FIG. 4, when mounting the same-surface electrode type group III nitride semiconductor light emitting device 1 in a shell type, one of the two frames (frame 31 in FIG. 4) The light emitting element 1 is bonded, the negative electrode of the light emitting element 1 (see reference numeral 19 shown in FIG. 3) is bonded to the frame 32 with a wire 34, and the positive electrode bonding pad of the light emitting element 1 (see reference numeral 18 shown in FIG. 3) is attached. The wire 33 is joined to the frame 31. Then, by sealing the periphery of the light emitting element 1 with a mold 35 made of a transparent resin, a bullet-type lamp 3 as shown in FIG. 4 can be created.

  Further, the group III nitride semiconductor of which conductivity is controlled by adding a dopant according to the present invention is not limited to the light emitting element as described above, but also a photoelectric conversion element such as a laser element or a light receiving element, or an HBT or HEMT. It can also be used for electronic devices such as. Many of these semiconductor elements have various structures, and the element structure of the group III nitride semiconductor multilayer structure according to the present invention is not limited at all including these known element structures.

  Next, the method for producing a group III nitride semiconductor and the method for producing a group III nitride semiconductor light-emitting device of the present invention will be described in more detail with reference to examples. However, the present invention is limited only to these examples. It is not a thing.

[Example 1]
FIG. 1 is a schematic cross-sectional view of a laminated semiconductor of a group III nitride compound semiconductor light-emitting device manufactured in Example 1.
In this example, a single crystal layer made of AlN is formed as the buffer layer 12 on the c-plane of the substrate 11 made of sapphire using RF sputtering, and a single crystal GaN is formed thereon as the n-type semiconductor layer 14. The underlayer 14a made of was formed by MOCVD, and the n-type contact layer 14b and the n-type clad layer 14c were formed on the underlayer 14a by RF sputtering. Then, the light emitting layer 15 is formed thereon by MOCVD, and the p-type cladding layer 16a and the p-type contact layer 16b are formed as the p-type semiconductor layer 16 on the light-emitting layer 15 by using the RF sputtering method. Lamination was performed in this order to produce a laminated semiconductor sample.

"Formation of buffer layer"
First, a substrate 11 made of (0001) c-plane sapphire having a diameter of 2 inches whose surface was mirror-polished was washed with hydrofluoric acid and an organic solvent, and then introduced into the chamber of the sputtering apparatus. At this time, as the sputtering apparatus, an apparatus including a high-frequency power supply unit and a mechanism capable of moving a position where a magnetic field is applied by rotating a magnet in the target was used.

  Then, the substrate 11 is heated to 500 ° C. in the chamber of the sputtering apparatus, nitrogen gas is introduced at a flow rate of 15 sccm, the pressure in the chamber is maintained at 1.0 Pa, and a high frequency bias of 50 W is applied to the substrate 11. The surface of the substrate 11 was cleaned by exposing it to nitrogen plasma.

  Next, after introducing argon and nitrogen gas into the chamber, the temperature of the substrate 11 was lowered to 500 ° C. Then, no bias is applied to the substrate 11 side, high frequency power of 2000 W is applied to the metal Al target side, the pressure in the furnace is maintained at 0.5 Pa, Ar gas is flowed at 5 sccm, and nitrogen gas is circulated at a flow rate of 15 sccm. The buffer layer 12 made of AlN was formed on the substrate 11 made of sapphire under the above conditions (the ratio of nitrogen to the whole gas was 75%). The growth rate at this time was 0.12 nm / s.

  The magnet in the target was rotated both when the substrate 11 was cleaned and when the buffer layer 12 was formed. As described above, after forming a buffer layer made of 50 nm of AlN, the generation of plasma was stopped. Through the above procedure, a buffer layer 12 made of single crystal AlN having a thickness of 50 nm was formed on the substrate 11.

"Formation of underlayer"
Next, the substrate 11 on which the buffer layer 12 was formed was transferred into the chamber of the MOCVD apparatus in order to grow an underlayer made of GaN by MOCVD. Then, the temperature of the substrate was raised to 1050 ° C. with hydrogen gas flowing through the chamber, and the dirt adhering to the surface of the buffer layer 12 was sublimated and removed. At this time, ammonia was circulated in the furnace when the temperature of the substrate 11 reached 830 ° C. or higher.

  Next, after the temperature of the substrate 11 is lowered to 1020 ° C., the vapor of trimethylgallium (TMG) generated by bubbling is circulated into the furnace while ammonia is circulated in the chamber as it is, and is made of single crystal GaN. The underlayer 14a was formed with a film thickness of 2 μm. Thereafter, the supply of TMG was stopped, the growth of GaN was stopped, and the temperature was lowered.

“Formation of n-type contact layer and n-type cladding layer”
Next, the substrate 11 on which the base layer 14a was formed was transferred into the chamber 41 of the sputtering apparatus 40 as shown in FIG. 5, and the n-type contact layer 14b made of GaN was formed by using the RF sputtering method. Here, the sputtering apparatus 40 used for the GaN film formation has a high-frequency power supply unit and a mechanism capable of moving the position where the magnetic field is applied by sweeping the magnet inside the square Ga target. I used something. At this time, a pipe for circulating the refrigerant was installed in the Ga target, and the refrigerant cooled to 20 ° C. was circulated in the pipe to prevent melting of Ga due to heat.

Next, after introducing argon and nitrogen gas into the chamber 41, the temperature of the substrate 11 was raised to 1000 ° C. Then, a high-frequency power of 2000 W was applied to the target 47 made of metal Ga, and Ar gas was circulated at a flow rate of 5 sccm and nitrogen gas at a flow rate of 15 sccm while maintaining the pressure in the furnace at 0.5 Pa (relative to the entire gas). The n-type contact layer 14b made of GaN was formed on the base layer 14a. At this time, a dopant element made of Si is disposed in a dopant container 50 provided in communication with the chamber 41, and the Si element is heated and vaporized by energization of the heater 53, and is supplied into the chamber 41. Thus, Si was doped into the GaN crystal forming the n-type contact layer 14b. The growth rate at this time was approximately 2 μm / s. Then, after forming the n-type contact layer 14b made of GaN, the generation of plasma was stopped.
By the above procedure, an n-type contact layer 14b made of Si-doped GaN having an electron concentration of 1 × 10 ¹⁹ cm ⁻³ and a thickness of 2 μm was formed.

Next, on the n-type contact layer 14b of the sample prepared in the above procedure, the same sputtering apparatus 40 is used, and the same procedure is used to have an Si concentration of 1 × 10 ¹⁸ cm ⁻³ and a thickness of 20 nm. An n-type cladding layer 14c made of GaN was formed.

Through the steps described above, the buffer layer 12 having a single crystal structure and made of AlN is formed on the substrate 11, and the undoped underlayer 14a having a thickness of 2 μm is formed on the buffer layer 12 and 1 × 10 ¹⁹ cm. A 2 μm Si-doped n-type contact layer 14b having a carrier concentration of ⁻³ is formed, and a 20 nm Si-doped n-type cladding layer 14c having a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ is formed thereon. did. The substrate taken out of the chamber after film formation was colorless and transparent, and the surface of the GaN layer (here, n-type cladding layer 14c) was a mirror surface.

"Formation of light emitting layer"
Next, on the n-type cladding layer 14c of the sample produced by the above procedure, a MOCVD method is used to form a barrier layer 15a made of GaN and a well layer 15b made of In _0.2 Ga _0.8 N. A light emitting layer 15 having a multiple quantum well structure was formed. In forming the light emitting layer 15, a barrier layer 15a is first formed on the n-type clad layer 14c made of Si-doped GaN, and made of In _0.2 Ga _0.8 N on the barrier layer 15a. A well layer 15b was formed. After repeating such a stacking procedure five times, a sixth barrier layer 15a is formed on the fifth stacked well layer 15b, and the barrier layers 15a are arranged on both sides of the light emitting layer 15 having a multiple quantum well structure. The structure was as follows.

  That is, the barrier layer 15a made of GaN having a thickness of 150 mm was formed by supplying ammonia, TEG, and monosilane to the furnace while the substrate temperature was set to 750 ° C. and nitrogen gas carrier was circulated.

Next, after the growth of the barrier layer 15a is completed, the temperature of the substrate 11, the pressure in the furnace, the flow rate and type of the carrier gas remain unchanged, and the TEG and TMI valves are switched to supply TEG and TMI into the furnace. A well layer 15b made of In _0.2 Ga _0.8 N was grown. As a result, a well layer 15b having a thickness of 20 mm was formed.

  After the growth of the well layer 15b was completed, the barrier layer 15a was grown again. Then, by repeating such a procedure five times, five barrier layers 15a and five well layers 15b were formed. Further, a barrier layer 15 a was formed on the well layer 15 b that was finally stacked, thereby forming the light emitting layer 15.

“Formation of p-type cladding layer and p-type contact layer”
The wafer obtained by each process described above is transferred into the sputtering apparatus 40 used for forming the n-type contact layer 14b and the n-type cladding layer 14c, and the p-type semiconductor layer 16 ( A p-type cladding layer 16a and a p-type contact layer 16b) were formed. At this time, as a target, both a target made of Al element and a target made of Ga element were placed in the chamber, and power was simultaneously applied to them, so that 5 nm of Mg was doped on the light emitting layer 15. A p-type cladding layer 16a made of Al _0.1 Ga _0.9 N is formed, and a p-type contact layer 16b made of Mg-doped Al _0.02 Ga _0.98 N having a thickness of 200 nm is formed thereon. Then, the p-type semiconductor layer 16 was formed.

First, after introducing argon and nitrogen gas into the chamber, the substrate temperature was raised to 1000 ° C. Next, a high frequency power of 2000 W is applied to the metal Ga target side, a high frequency power of 500 W is applied to the Al target, and Ar gas is circulated at a flow rate of 8 sccm and nitrogen gas at a flow rate of 12 sccm while maintaining the pressure in the furnace at 0.5 Pa. The p-type cladding layer 16a was formed under the above conditions (the ratio of nitrogen to the total gas was 60%). At this time, a dopant element made of Mg is disposed in a dopant container 50 provided in communication with the chamber 41, and the Mg element is heated and vaporized by energization of the heater 53, and is supplied into the chamber 41. Thus, Mg was doped into the Al _0.1 Ga _0.9 N crystal forming the p-type cladding layer 16a. The growth rate at this time was approximately 0.2 nm / s. Then, after forming the p-type cladding layer 16a made of Al _0.1 Ga _0.9 N, the generation of plasma was stopped.
By the above procedure, a p-type cladding layer 16a made of Al _0.1 Ga _0.9 N doped with 5 nm of Mg was formed.

Next, a p-type contact layer 16b made of Mg-doped Al _0.02 Ga _0.98 N having a thickness of 200 nm is formed on the p-type cladding layer 16a produced by the above procedure by the same procedure using the same sputtering apparatus 40. A p-type semiconductor layer 16 was formed by film formation.
Then, after forming the p-type contact layer 16b made of Mg-doped AlGaN, the plasma generation was stopped, and the wafer was transferred out of the sputtering apparatus 40 together with the wafer tray through the load lock chamber.
The p-type contact layer 16b made of Mg-doped AlGaN obtained in the above process exhibits p-type without an annealing process for activating p-type carriers, and the carrier concentration is 3 × 10 ¹⁶ pieces / cm 3. ³ .

  Through such a process, an epitaxial wafer (laminated semiconductor 10) having an epitaxial layer structure for a group III nitride compound semiconductor light emitting device as shown in FIG. 1 was finally produced.

The epitaxial wafer for LED produced as described above has an AlN layer (buffer layer 12) having a single crystal structure on a substrate 11 made of sapphire having a c-plane, like the laminated semiconductor 10 shown in FIG. After forming, in order from the substrate 11 side, a 2 μm undoped GaN layer (underlayer 14 a), a 2 μm Si doped GaN layer (n-type contact layer 14 b) having an electron concentration of 1 × 10 ¹⁹ cm ⁻³ , 1 × 10 20-nm GaN clad layer (n-type clad layer 14c) having an electron concentration of ¹⁸ cm ⁻³ , 6 layers of GaN barrier layers (barrier layer) having a thickness of 150 mm starting from the GaN barrier layer and ending at the GaN barrier layer and 15a), a multiple quantum well structure consisting of layer thickness non-doped _in 0.2 _{Ga 0.8} N well layer of the five layers was set to 20Å and (well layer 15b) (the light emitting layer 15 , Layered Mg-doped _Al 0.1 _{Ga 0.9} N layer having a film thickness of 5nm and (p-type cladding layer 16a), a thickness of 200 nm Mg-doped _Al 0.02 _{Ga 0.98} N to (p-type contact layer 16b) Has the structure.

"Production of LED"
Subsequently, LED was produced using the said epitaxial wafer (laminated semiconductor 10).
That is, the transparent electrode 17 made of ITO is formed on the surface of the Mg-doped AlGaN layer (p-type semiconductor layer 16b) of the epitaxial wafer by a known photolithography technique, and titanium, aluminum, and gold are sequentially formed thereon. A positive electrode bonding pad 18 (p-electrode bonding pad) having a laminated structure was formed as a p-side electrode. Further, dry etching is performed on the wafer to expose a region for forming the n-side electrode (negative electrode) of the n-type contact layer 14b, and four layers of Ni, Al, Ti, and Au are sequentially laminated on the exposed region 14d. A negative electrode 19 (n-side electrode) was formed. By such a procedure, each electrode having a shape as shown in FIG. 2 was formed on the wafer (see the laminated semiconductor 10 in FIG. 1).

And about the wafer in which each electrode of p side and n side was formed in the above-mentioned procedure, the back surface of the board | substrate 11 which consists of sapphire was ground and grind | polished, and it was set as the mirror-shaped surface. Then, this wafer was cut into a 350 μm square chip, placed on the lead frame so that each electrode was on top, and connected to the lead frame with a gold wire to form a light emitting element (the lamp 3 in FIG. reference).
When a forward current was passed between the p-side and n-side electrodes of the light-emitting diode produced as described above, the forward voltage at a current of 20 mA was 3.0V. Moreover, when the light emission state was observed through the p side translucent electrode 17, the light emission wavelength was 460 nm and the light emission output showed 14.0 mW. Such characteristics of the light-emitting diode were obtained with no variation for light-emitting diodes manufactured from almost the entire surface of the manufactured wafer.

[Example 2]
In Example 2, the buffer layer formed on the substrate 11 is formed in a polycrystalline structure as an aggregate of columnar crystals made of AlN by controlling the film forming conditions as follows. The buffer layer and each semiconductor layer were formed on the substrate 11 by the same method as described above.
At this time, as conditions for cleaning the surface of the substrate 11 by exposure to nitrogen plasma, the substrate temperature is 750 ° C., the pressure in the chamber is 0.08 Pa, and the film formation conditions for the buffer layer made of AlN are Ar The conditions are different from the conditions shown in Example 1 in that the flow rate is 15 sccm for gas and 5 sccm for nitrogen gas (the ratio of nitrogen to the total gas is 25%).

By such a process, a buffer layer made of AlN as an aggregate of columnar crystals is formed on the substrate 11, and an undoped base layer 14a having a thickness of 2 μm and a carrier of 1 × 10 ¹⁹ cm ⁻³ are formed thereon. A 2 μm Si-doped n-type contact layer 14b having a concentration was formed, and a 20 nm Si-doped n-type cladding layer 14c having a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ was formed thereon. The substrate taken out of the chamber after film formation was colorless and transparent, and the surface of the GaN layer (here, n-type cladding layer 14c) was a mirror surface.
Further, after forming the respective layers constituting the semiconductor layer by the same method as in Example 1, the electrical characteristics of the p-type contact layer 16b made of Mg-doped AlGaN were confirmed, and it was found that the p-type carriers were activated. A p-type was exhibited even without annealing, and the carrier concentration was 3 × 10 ¹⁶ / cm ³ .

  Further, when a forward current was passed between the p-side and n-side electrodes of a light emitting diode fabricated using such a wafer, the forward voltage at a current of 20 mA was 3.0V. Moreover, when the light emission state was observed through the p side translucent electrode 17, the light emission wavelength was 460 nm and the light emission output showed 14.0 mW. Such characteristics of the light-emitting diode were obtained with no variation for light-emitting diodes manufactured from almost the entire surface of the manufactured wafer.

[Comparative example]
In the comparative example, a doping container communicating with the inside of the chamber is not provided, and a fine Ga is mixed with liquid Ga, which is poured into a target tray and hardened and installed in the chamber. Film formation similar to the example except that the Si-doped n-type contact layer and n-type clad layer, Mg-doped p-type clad layer and p-type contact layer were formed using the sputtering apparatus employing the method. Under the conditions, a stacked semiconductor sample as shown in FIG. 1 was manufactured.

In the comparative example, the substrate taken out from the chamber after forming the n-type cladding layer was colorless and transparent, and the surface was a mirror surface.
In addition, the sample taken out from the chamber after the formation of the p-type contact layer shows that the p-type contact layer made of Mg-doped AlGaN shows p-type without performing annealing treatment for activating p-type carriers, The carrier concentration was 3 × 10 ¹⁶ pieces / cm ³ .

Then, a transparent positive electrode, a positive electrode bonding pad, and a negative electrode are formed on the laminated semiconductor sample in the same procedure as in the example, and the back surface of the substrate made of sapphire is ground and polished to form a mirror-like surface. . The wafer was cut into 350 μm square chips, placed on the lead frame so that each electrode was on top, and connected to the lead frame with a gold wire to obtain a light emitting device.
When a forward current was passed between the p-side and n-side electrodes of the light emitting diode of the comparative example produced as described above, the forward voltage at a current of 20 mA was 3.2V. Moreover, when the light emission state was observed through the p side translucent electrode 17, the light emission wavelength was 460 nm and the light emission output showed 13.8 mW. Such characteristics of the light-emitting diode were obtained with no variation for light-emitting diodes manufactured from almost the entire surface of the manufactured wafer.

As shown in the above results, there was no significant difference in the characteristics of the light emitting elements of the example and the comparative example. However, in the comparative example, the film formation process was performed 50 times until the sputter target was used up. In this case, the characteristics of the manufactured light-emitting element gradually deteriorated as the number of film formations increased. . In particular, in the sample of the light emitting element manufactured by performing the 50th film formation, the driving voltage (forward voltage) increased to 3.4V. And after the film-forming process of 50 times, when the inside of the chamber of a sputter | spatter apparatus was inspected, the mode that Ga of a sputter | spatter target resolidified after liquefying was recognized. In the comparative example, it is considered that due to this influence, a phenomenon in which the dopant element aggregates near the surface of the target occurs and is selectively consumed, leading to deterioration of the characteristics of the light emitting element.
After this, when the sputtering target was replaced and the film formation process was performed under the same conditions, the light emitting element manufactured first after the target replacement had a driving voltage (forward voltage) of 3.0 V, before the target replacement. It was confirmed that the characteristics were different from those of the light emitting element. As described above, in the conventional method in which the target composed of the dopant element is installed in the chamber in the same manner as the Ga-containing target, the doping amount fluctuates as the target is used in the film formation process, and the sputter target is replaced. It has become clear that variations in the characteristics of the light emitting element occur for each target.

  From the above results, it is clear that the group III nitride semiconductor according to the present invention has excellent device characteristics, and that the group III nitride semiconductor light emitting device according to the present invention has excellent light emission characteristics.

  Since the group III nitride semiconductor manufacturing method of the present invention can produce a group III nitride semiconductor whose conductivity is optimally controlled by adding a dopant by sputtering, a light emitting diode (LED) or laser diode ( LD) p-type contact layer and various semiconductor elements such as an electronic device such as an FET.

It is a figure which illustrates typically an example of the group III nitride semiconductor concerning the present invention, and is a schematic diagram showing the section structure of a lamination semiconductor. It is a figure which explains typically an example of the group III nitride semiconductor concerning the present invention, and is a schematic diagram showing the plane structure of the light emitting element constituted by the group III nitride semiconductor. It is a figure which explains typically an example of the group III nitride semiconductor concerning the present invention, and is a schematic diagram showing the section structure of the light emitting element constituted by the group III nitride semiconductor. It is the schematic explaining typically the lamp | ramp comprised using the group III nitride semiconductor light-emitting device based on this invention. It is a figure which illustrates typically an example of the manufacturing method of the group III nitride semiconductor light-emitting device based on this invention, and is the schematic which shows the structure of the sputtering device provided with the dopant container connected in a chamber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Group III nitride semiconductor light-emitting device, 10 ... Laminated semiconductor (Group III nitride semiconductor), 11 ... Substrate, 11a ... Surface, 12 ... Buffer layer, 14 ... N-type semiconductor layer, 15 ... Light emitting layer, 16 ... p Type semiconductor layer (group III nitride semiconductor), 16a ... p-type cladding layer, 16b ... p-type contact layer, 3 ... lamp, 40 ... sputtering device, 41 ... chamber, 47 ... target, 50 ... dopant container, 51 ... dopant Element (donor impurity, acceptor impurity), 52a ... control valve (flow rate control means), 53 ... heater

Claims (15)

In this method, a substrate and a target containing Ga element are arranged in a chamber, and a single crystal group III nitride semiconductor doped with a dopant is formed on the substrate by a reactive sputtering method. And
The group III nitride is provided by disposing a dopant element in a dopant container provided outside the chamber and communicating with the inside of the chamber, and vaporizing the dopant element in the dopant container and supplying the dopant element into the chamber. A method for producing a group III nitride semiconductor, comprising adding the dopant to a metal semiconductor.   The method for producing a group III nitride semiconductor according to claim 1, wherein the dopant element disposed in the dopant container is heated to vaporize the dopant element and supply the dopant element into the chamber.   3. The supply amount of the dopant element vaporized in the dopant container into the chamber is adjusted by providing a flow rate control means between the dopant container and the chamber. The manufacturing method of the group III nitride semiconductor of description.   The atmosphere in the chamber when forming the group III nitride semiconductor is a gas atmosphere containing a nitrogen atom-containing gas in a range of 20 to 80% and the balance containing at least an inert gas. The method for producing a group III nitride semiconductor according to any one of claims 1 to 3, wherein: 5. The III according to claim 4, wherein the nitrogen atom-containing gas present in the gas atmosphere in the chamber is nitrogen gas (N ₂ ), and the inert gas is argon gas (Ar). A method for producing a group nitride semiconductor.   The group III nitride according to any one of claims 1 to 5, wherein a temperature of the substrate in forming the group III nitride semiconductor is in a range of 600 ° C to 1050 ° C. Semiconductor manufacturing method.   The method for producing a group III nitride semiconductor according to any one of claims 1 to 6, wherein the dopant element comprises a donor impurity.   The group III nitride semiconductor manufacturing method according to claim 7, wherein the donor impurity is a silicon (Si) element.   The ratio of the Ga element and the Si element in the atmospheric gas in the chamber when forming the group III nitride semiconductor is in the range of 1: 0.0001 to 1: 0.00001. A method for producing a group III nitride semiconductor according to claim 8.   The method for producing a group III nitride semiconductor according to any one of claims 1 to 6, wherein the dopant element comprises an acceptor impurity.   The group III nitride semiconductor manufacturing method according to claim 10, wherein the acceptor impurity is a magnesium (Mg) element.   The ratio of Ga element and Mg element in the atmospheric gas in the chamber when forming the group III nitride semiconductor is in a range of 1: 0.01 to 1: 0.0001. The method for producing a group III nitride semiconductor according to claim 11. A single crystal III comprising a semiconductor layer in which an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer each made of a group III nitride semiconductor are sequentially stacked, and at least a part of the n-type semiconductor layer is doped with a donor impurity. A method for producing a group III nitride semiconductor light-emitting device comprising a group nitride semiconductor, wherein at least a part of the p-type semiconductor layer comprises a single crystal group III nitride semiconductor to which an acceptor impurity is added,
A step of forming at least a part of the n-type semiconductor layer by the group III nitride semiconductor manufacturing method according to claim 7 and / or at least a part of the p-type semiconductor layer. Forming a group III nitride semiconductor according to any one of claims 10 to 12 by the method for manufacturing a group III nitride semiconductor according to any one of claims 10 to 12.   A group III nitride semiconductor light-emitting device obtained by the manufacturing method according to claim 13.   A lamp comprising the group III nitride semiconductor light-emitting device according to claim 14.

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