JP2005045054A - Group III nitride semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a defect rate of a light emitting element for extracting light from the substrate side and improve light extraction efficiency in a group III nitride semiconductor light emitting element using an n-type conductive substrate, and to provide a group III nitride semiconductor on an industrial scale. Aim for mass production of light emitting devices.
A group III nitride semiconductor light emitting device of the present invention comprises a group III nitride semiconductor film and a p-type electrode on a light-transmitting n-type semiconductor substrate having conductivity, and an n-type semiconductor substrate. A light-emitting element for extracting light, wherein at least part of the surface of the group III nitride semiconductor film opposite to the light extraction direction, at least part of the side surface of the group III nitride semiconductor film and the side surface of the n-type semiconductor substrate And an insulating protective film.
[Selection] Figure 1

Description

  The present invention relates to a group III nitride semiconductor light emitting device fabricated on a conductive semiconductor substrate.

Conventionally, group III nitride semiconductors typified by GaN and the like have been used or studied as light-emitting elements and high-power devices using their characteristics. For example, when a light-emitting element is manufactured, it can be technically used as a light-emitting element having a wide width from purple to orange by adjusting the constituent composition. In recent years, blue light emitting diodes or green light emitting diodes have been put to practical use by utilizing the characteristics, and blue-violet semiconductor lasers have been developed as semiconductor laser elements. In the present specification, the group III nitride semiconductor refers to a group III-V compound semiconductor in which a group V element is nitrogen, for example, GaN, AlN, Al _α Ga _1-α N (0 <α <1), refers _{InN, In β Ga 1-β} N (0 <β <1), In γ Ga δ Al 1-γ-δ N (0 <γ <1, (0 <δ <1) and ( Hereinafter also referred to as “GaN compound semiconductor”).

  When manufacturing a GaN-based compound semiconductor film, a substrate such as sapphire, SiC, spinel, Si, or GaAs is used as a substrate (see Patent Document 1). For example, when sapphire is used as a substrate, a GaN or AlN buffer layer is formed in advance at a low temperature of 500 ° C. to 600 ° C. before epitaxial growth of the GaN film, and then the substrate is formed at 1000 ° C. to 1100 ° C. When the GaN-based compound semiconductor film is epitaxially grown at a high temperature, a structurally and electrically good crystal having a good surface state can be obtained. Since the substrate is insulative, two electrodes are formed on the surface. A light emitting element can be obtained by forming.

  Further, when SiC is used as a substrate, a good crystal can be obtained by using a thin AlN film as a buffer layer at a growth temperature for epitaxial growth. Since SiC is a conductive substrate, the substrate back surface and the epitaxial growth surface can be obtained. It is known that light-emitting elements each having an electrode can be obtained. Further, since the sapphire substrate is transparent to light from purple to orange, it is known that two electrodes are formed on the surface and a light extraction structure (flip chip structure) from the substrate can be employed (see Patent Document 2). ).

In general, GaN and SiC cannot obtain a p-type low resistance, and are used as an n-type substrate. When a GaN-based compound semiconductor light emitting device is formed by epitaxial growth using an n-type substrate, the growth end surface becomes p-type, and GaN cannot obtain a p-type low-resistance film. ) An electrode is used. Such a translucent electrode has a thin film thickness of about 2 nm to 10 nm and a narrow range of conditions. Therefore, it is difficult to obtain ohmic characteristics, and the uniformity of the electrode characteristics for each manufactured light emitting element is not good. Furthermore, there is a problem that the yield decreases due to the heat treatment step of the electrodes. Moreover, the translucent electrode has a transmittance of 50 to 60% of the emitted light, and the external extraction efficiency is not good. Therefore, even when a conductive substrate is used, an attempt is made to extract light from the substrate side.
Japanese Patent Laid-Open No. 10-114600 JP-A-10-150220

  However, when the p-type electrode is connected to a stem or the like and light is extracted from the substrate side, the position of the p-type electrode and the pn junction is close to 0.1 μm or less in the GaN-based light emitting device. It needs to be protected. In addition, when the upper and lower electrodes are formed using the conductive substrate, the chip size can be reduced as compared with the case of the front surface two electrodes, but the electrode (external connection electrode such as a pad electrode) is smaller than the chip size. Therefore, it is necessary to suppress the inhibition of light extraction by the electrode and increase the external quantum efficiency.

  The group III nitride semiconductor light emitting device of the present invention includes a group III nitride semiconductor film and a p-type electrode on a light-transmitting n-type semiconductor substrate having conductivity, and extracts light from the n-type semiconductor substrate. A light emitting device having an insulating property on at least a part of a surface of the group III nitride semiconductor film opposite to the light extraction direction, at least a part of a side surface of the group III nitride semiconductor film and a side surface of the n-type semiconductor substrate. It is characterized by having a protective film.

  According to the present invention, in a GaN-based compound semiconductor light-emitting device using an n-type conductive substrate, it is possible to reduce the defect rate of the light-emitting device that extracts light from the substrate side and to improve the light extraction efficiency on an industrial scale. Mass production of GaN-based compound semiconductor light-emitting elements becomes possible.

  The group III nitride semiconductor light-emitting device of the present invention typically has an n-type GaN layer 3 on a conductive translucent n-type semiconductor substrate such as a GaN thick film substrate 2 as shown in FIG. A light emitting device comprising a group III nitride semiconductor film comprising a light emitting layer 4, a p-type cladding layer 5, a p-type contact layer 6 and the like, and a p-type electrode 11, and for extracting light from an n-type semiconductor substrate, An insulating protective film 13 is provided on at least a part of the surface of the group nitride semiconductor film opposite to the light extraction direction, at least a part of the side surface of the group III nitride semiconductor film and the side surface of the n-type semiconductor substrate. It is characterized by. By providing such a protective film, the pn junction and the substrate can be protected, the defect rate of the light emitting element can be reduced, and the GaN compound semiconductor element can be mass-produced.

Since it is necessary to form a film that effectively protects from the p-type growth layer to the n-type semiconductor substrate, the protective film on the side surface is preferably formed at least 10 μm from the surface of the group III nitride semiconductor film, and is formed at least 15 μm. It is more preferable. On the other hand, the side surface is formed by etching or the like, and a protective film is formed on the side surface of the formed hole. Therefore, since formation becomes difficult if it is too deep, it is preferable that the protective film on the side surface be a region not larger than the thickness of the n-type semiconductor substrate, and more preferably not more than ½ of the thickness of the substrate. Further, the thickness of the protective film is preferably 0.1 to 0.7 μm and more preferably 0.2 to 0.5 μm in order to effectively protect the pn junction and the substrate. The material for forming the protective film is preferably SiO ₂ , Al ₂ O ₃ , SiN, or the like because it has sufficient strength and insulation. By making the protective film electrically insulating, leakage current on the side surface of the light emitting element can be suppressed. For example, after forming a group III nitride semiconductor film on the n-type semiconductor substrate, the protective film forms a groove by etching or dicing from the surface of the group III nitride semiconductor film to the n-type semiconductor substrate. It can be easily formed on the end face by plasma CVD or the like.

  Since the light-emitting element of the present invention takes out light from an n-type semiconductor substrate, the n-type semiconductor substrate uses a light-transmitting material. Among light-transmitting materials, light having a wavelength of 400 nm or more is transmitted. Those that do are preferred. This is because light having a wavelength of less than 400 nm corresponds to radiation such as ultraviolet rays or X-rays, and the present invention mainly aims to provide a laser element that emits light in blue to orange colors. In addition, since the n-type semiconductor substrate used in the light emitting device of the present invention needs to have conductivity, a substrate made of a group III nitride such as GaN or SiC is preferably used. The group III nitride semiconductor substrate can be easily manufactured by forming it on the base substrate by an epitaxial growth method, and then removing a part or all of the base substrate by peeling, polishing, or etching.

When a group III nitride semiconductor substrate is used as the n-type semiconductor substrate, the carrier concentration is preferably 1 × 10 ¹⁸ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less. When the carrier concentration is less than 1 × 10 ¹⁸ cm ⁻³ , the operating voltage tends to increase. On the other hand, if the carrier concentration is higher than 5 × 10 ¹⁹ cm ⁻³ , the light emission output tends to be reduced because the light emission output is absorbed by the substrate. Similarly, when an SiC semiconductor substrate is used as the n-type semiconductor substrate, a substrate having a carrier concentration of 5 × 10 ¹⁶ cm ⁻³ or more is preferable in order to reduce the operating voltage, and in order to increase the light emission output, the carrier concentration is increased. Is preferably a substrate of 1 × 10 ¹⁸ cm ⁻³ or less.

Since the n-type semiconductor substrate has a low carrier concentration and the current cannot be effectively spread only by the substrate, the n-type semiconductor substrate preferably has a mesh-shaped n-type electrode on the light extraction surface, and a pad for external connection is provided on the light extraction surface. What has an electrode is preferable. In order not to hinder the extraction of light, the n-type electrode preferably has translucency. Examples of materials having translucency and conductivity include ITO, IDIXO, and ZnO, and such materials are suitable as materials for n-type electrodes. On the other hand, it is preferable that the pad electrode has a current blocking structure at a portion in contact with the n-type electrode. By setting it as this aspect, light emission just under a pad electrode decreases, the light extraction inhibiting effect by a pad electrode can be reduced, and luminous efficiency can be improved. In order to make the pad electrode have a current blocking structure, for example, in addition to a mode in which an insulating film such as SiO ₂ , Al ₂ O ₃ , or SiN is formed in a portion in contact with the n-type electrode, a mode in which a current blocking structure by a pn junction is used However, the same effect can be obtained. Further, the insertion position of the current blocking layer is also effective immediately above the substrate.

  The group III nitride semiconductor film formed on the n-type semiconductor substrate preferably has an uneven portion in contact with the p-type electrode. By providing irregularities in the portion in contact with the p-type electrode, light scattering occurs and the light extraction efficiency is improved. The unevenness is preferably 10 nm to 500 nm in terms of arithmetic average roughness. If it is less than 10 nm, the light scattering effect is small, and the light emission output does not increase sufficiently. On the other hand, if the thickness is larger than 500 nm, the unevenness is too large, so that a good ohmic contact with the p-type electrode cannot be obtained. Note that the p-electrode can be used as a common electrode.

Example 1
In this example, a thick GaN film grown on the sapphire substrate using the H-VPE method was used as the substrate. First, a sapphire substrate having a (0001) plane was washed, and an undoped GaN film having a thickness of about 3 μm was grown as an underlayer by MOCVD using the following procedure. The cleaned sapphire substrate was introduced into the MOCVD apparatus and cleaned at a high temperature of about 1100 ° C. in an H ₂ atmosphere. Thereafter, the temperature was lowered, and NH ₃ and trimethyl gallium (TMG) were introduced at 600 ° C. while flowing hydrogen (H ₂ ) as a carrier gas at 10 L / m, respectively, at a thickness of about 20 nm. A GaN low temperature buffer layer was grown.

Thereafter, the supply of TMG was once stopped, the temperature was raised again to about 1050 ° C., TMG was introduced at about 100 mol / m, and an undoped GaN film having a thickness of about 3 μm was grown in one hour. Thereafter, the supply of TMG and NH ₃ was stopped, the temperature was lowered to room temperature, and the sapphire substrate on which the undoped GaN underlayer was grown was taken out. The low temperature buffer layer is not limited to GaN, and trimethylaluminum (TMA), TMG, or NH ₃ may be used, and an AlN film or a GaAlN film may be used.

Next, in order to prevent cracks from occurring when a thick film is grown on the sapphire substrate on which the undoped GaN underlayer produced by the above method has been grown, a stripe shape having a thickness of 2000 mm, a width of 7 μm, and an interval of 10 μm is used. A growth suppression film was formed, and selective growth was performed by the H-VPE method to grow a flat GaN thick film. In this example, the growth suppression film used was a SiO ₂ film deposited by electron beam evaporation (EB method) etched using photolithography.

Subsequently, a GaN thick film was grown by the H-VPE method by the following method. A sapphire substrate on which an undoped GaN underlayer having a striped growth suppression film produced by the above-described method was grown was introduced into the H-VPE apparatus. The substrate temperature was raised to about 1050 ° C. while flowing N ₂ carrier gas and NH ₃ each at 5 L / m. Thereafter, GaCl was introduced at 100 cc / m on the substrate to start growing a thick GaN film. GaCl was generated by flowing HCl gas through Ga metal maintained at about 850 ° C. Further, impurity doping was arbitrarily performed during growth by flowing an impurity gas using an impurity doping line that was independently piped to the vicinity of the substrate.

In this example, for the purpose of doping Si, at the same time as starting growth, 200 nmol / m of monosilane (SiH ₄ ) was flowed to grow a Si-doped GaN layer (Si impurity concentration: 3.8 × 10 ¹⁸ cm ⁻³ ). Then, a GaN thick film having a thickness of 350 μm was obtained by growth for 3 hours. Regarding Si doping, other raw materials such as monochlorosilane (SiH ₃ Cl), dichlorosilane (SiH ₂ Cl ₂ ), and trichlorosilane (SiHCl ₃ ) may be used without being limited to SiH ₄ .

After the growth, the sapphire substrate, the undoped GaN film by the MOCVD method, and the SiO ₂ film were removed by polishing to obtain a GaN thick film substrate 2 (hereinafter also referred to as “GaN substrate”). Using the GaN thick film obtained as described above as a substrate, a light emitting device structure was grown by MOCVD. Hereinafter, a method for growing a GaN-based compound semiconductor LED on a GaN substrate will be described.

FIG. 1 shows a cross-sectional view of a GaN-based compound semiconductor LED manufactured by the method of this example. The GaN substrate was introduced into the MOCVD apparatus so that the surface opposite to the base removal surface was epitaxially grown, and the temperature was raised to about 1050 ° C. while flowing N ₂ and NH ₃ each at 5 L / m. When the temperature rose, the carrier gas was changed from N ₂ to H ₂ , TMG was introduced at 100 μmol / m, SiH ₄ was introduced at 10 nmol / m, and the n-type GaN layer 3 was grown by about 4 μm. Thereafter, the supply of TMG was stopped, the carrier gas was changed from H ₂ to N ₂ again, the temperature was lowered to 700 ° C., and trimethylindium (TMI) as an indium raw material was introduced at 10 μmol / m, and TMG was introduced at 15 μmol / m. Then, a 4 nm thick barrier layer made of In _0.05 Ga _0.95 N was grown. Thereafter, the supply amount of TMI was increased to 50 μmol / m, and a 2 nm-thick well layer made of In _0.2 Ga _0.8 N was grown. The well layer is grown in a total of three layers in the same manner, and a multiple quantum well (MQW) light emitting layer 4 is grown in which there are a total of four barrier layers between and on both sides of the well layer. did.

When the growth of MQW is finished, the supply of TMI and TMG is stopped, the temperature is raised again to 1050 ° C., the carrier gas is changed from N ₂ to H ₂ again, TMG is 50 μmol / m, TMA is 30 μmol / m, A p-type doping raw material biscyclopentadienylmagnesium (Cp ₂ Mg) was flowed at 10 nmol / m to grow a 20-nm-thick p-type Al _0.2 Ga _0.8 N cladding layer 5, and finally, supply of TMG Was adjusted to 100 μmol / m, the supply of TMA was stopped, the p-type GaN contact layer 6 having a thickness of 0.1 μm was grown, and the growth of the light emitting device structure was completed. When the growth was completed, the supply of TMG and Cp ₂ Mg was stopped, the temperature was lowered, and the film was taken out from the MOCVD apparatus at room temperature.

  Thereafter, the p-GaN contact layer 6 was etched up to the n-type GaN layer 3 using a dry etching apparatus to form a mesa. Thereafter, Pd was deposited on the p-GaN portion at 150 Å and Au was deposited at 1000 Å to form the p-type electrode 11. Further, the substrate temperature was kept at about 200 ° C., and 150 nm of Ti and 1000 mm of Al were deposited on the back surface of the GaN thick film substrate 2 to form the n-type electrode 21. The n-type electrode 21 was formed in a lattice shape having a line width of 50 μm. In addition, 3000 μg of Au was deposited on a part of the n-type electrode 21 to form the pad electrode 22.

Next, a groove 12 was formed from the epitaxial surface to the GaN thick film substrate 2 using a dicing apparatus. The depth of the groove was 20 μm and the width was 50 μm. Subsequently, an insulating protective film 13 made of silicon oxide (SiO ₂ ) having a thickness of 0.3 μm was formed on the epitaxial surface and the groove using a plasma CVD apparatus. As a result, as shown in FIG. 1, a part of the surface of the group III nitride semiconductor film opposite to the light extraction direction, a side surface of the group III nitride semiconductor film, and a part of the side surface of the n-type semiconductor substrate, An insulating protective film 13 was formed. Finally, the center of the groove 12 was separated by a cleaving or dicing method using a cutting blade (thickness 30 μm) thinner than the groove 12 so that the element length was about 200 μm. The produced LED was used by connecting a p-electrode to the stem using a conductive adhesive and forming an electrical connection using a wire bond to the n-type electrode.

  The LED manufactured in this embodiment has an operating voltage of 2.9 V, an emission wavelength of 470 nm, and an emission output of 2.5 mW. A life test of about 5000 hours was performed, but the decrease in the optical output was 10% or less. Good results were obtained. Further, the defect rate when the stem was placed was suppressed to 5% or less.

Comparative Example 1
As Comparative Example 1, an LED having a structure in which no protective film was formed was produced. The manufacturing method was the same as that of Example 1, and the groove was not formed, and the mesa forming portion was cut to perform element isolation. In the case of this element, the operating voltage is 2.9 V, the emission wavelength is 470 nm, the emission output is 2.5 mW, and there is no change in the characteristics, but due to the wraparound of the conductive adhesive, the defect rate on the stem mounting is There was 50%, and the variation in characteristics between elements was 10% or more.

Example 2
In this example, an LED was manufactured using a GaN substrate with a different carrier concentration. Except that the GaN thick film (Si-doped, carrier concentration: 5 × 10 ¹⁷ cm ⁻³ , thickness 350 μm) grown by the H-VPE method and exfoliated from the sapphire substrate was used as the substrate in the same manner as in Example 1. A light emitting device was fabricated in the same manner as in Example 1. This device had an emission wavelength of 470 nm and an optical output of 2.2 mW, and there was no change, but the operating voltage was as high as 3.3V.

Example 3
In this example, a light emitting device was manufactured in the same manner as in Example 1 except that a GaN thick film (Si-doped, carrier concentration: 7 × 10 ¹⁹ cm ⁻³ , thickness 350 μm) was used as a substrate. This element did not change with an operating voltage of 3.1 V and an emission wavelength of 470 nm, but the emission output was 2.0 mW, and the optical output was lowered due to absorption by the substrate.

Example 4
In this example, an example of a light-emitting element manufactured by forming a group III nitride semiconductor substrate on a base substrate by an epitaxial growth technique and then removing a part of the base substrate is shown. FIG. 2 shows a cross-sectional view of a GaN-based compound semiconductor LED manufactured by the method of this example. As shown in FIG. 2, this LED has a GaN thick film substrate 202, an n-type GaN layer 203, a light emitting layer 204, a p-type cladding layer 205, a p-type contact layer 206, p on a sapphire substrate 201 as a base substrate. A type electrode 211 is formed in this order, and a protective film 213 made of SiO ₂ is formed on a part of the surface of the p-type contact layer 206, a side surface of the group III nitride semiconductor film, and a part of the side surface of the GaN thick film substrate. ing. The sapphire substrate 201 has a structure in which an n-type electrode 221 and a pad electrode 222 are formed on the light extraction surface side. The protective film 213 was formed on the end face of the groove after forming the groove 212 from the surface of the p-type contact layer 206 to the GaN thick film substrate 202.

  In the same manner as in Example 1, a 350 μm thick GaN film 202 was grown on the sapphire substrate by the H-VPE method. Subsequently, a light emitting element structure (up to the p-type GaN contact layer 206) was formed on the GaN thick film 202 with the sapphire attached by using the MOCVD method in the same manner as in Example 1. Thereafter, the p-GaN contact layer 206 was etched up to the n-type GaN layer 203 using a dry etching apparatus to form a mesa.

Thereafter, Pd was deposited on the p-GaN contact layer 206 by 150 to 1000 and Au to 1000 to form a p-type electrode 211. Next, a SiO ₂ mask was formed on a part of the sapphire substrate, and the sapphire substrate was removed by etching from the back surface to the GaN thick film substrate 202 using a dry etching apparatus. Subsequently, on the etching surface of the GaN thick film substrate 202 and the sapphire substrate 201, 300 nm of Ti and 1000 mm of Al were deposited to form an n-type electrode 221. The n-type electrode 221 was formed in a lattice shape having a line width of 50 μm. In addition, a pad electrode 222 was formed on a part of the n-type electrode 221 by depositing 3000 μg of Au.

  The LED manufactured in this example has an operating voltage of 2.9 V, an emission wavelength of 470 nm, and an emission output of 2.8 mW. A life test of about 5000 hours was carried out, but the decrease in the optical output was 10% or less, which was good. Results were obtained. Further, the defect rate when the stem was placed was suppressed to 5% or less. In this embodiment, the light output can be improved due to the narrowing effect due to the pad electrode formed on the sapphire substrate as an insulator and the n-type electrode formed on a part of the GaN thick film substrate.

Example 5
In this example, the LED characteristics when an unevenness is formed on the surface of the p-type GaN contact layer in the LED manufactured by the method shown in Example 1 will be described. FIG. 3 shows a cross-sectional view of a GaN-based compound semiconductor LED manufactured by the method of this example. In this LED, as shown in FIG. 3, an n-type GaN layer 303, a light emitting layer 304, a p-type cladding layer 305, a p-type contact layer 306, and a p-type electrode 311 are formed in this order on a GaN thick film substrate 302. The surface of the p-type contact layer 306 has irregularities 306b, and SiO ₂ is formed on a part of the surface of the p-type contact layer 306, a side surface of the group III nitride semiconductor film, and a part of the side surface of the n-type semiconductor substrate. A protective film 313 made of is formed. Further, an n-type electrode 321 and a pad electrode 322 are formed on the light extraction surface side of the GaN thick film substrate 302. The protective film 313 was formed on the end face of the groove after forming the groove 312 from the p-type contact layer 306 to the GaN thick film substrate 302.

  The layers up to the p-type GaN contact layer 306 were formed by the MOCVD method according to the method shown in Example 1. Subsequently, using a polishing apparatus, the surface of the p-type GaN contact layer 306 was roughened, and irregularities 306b were formed on the surface. For the formation of irregularities, diamond abrasive grains having a particle size of 3 μm were used, and irregularities with an arithmetic average roughness of 100 nm were formed. Thereafter, an LED was produced in the same manner as in Example 1.

  The LED manufactured in this example has an operating voltage of 2.9 V, a light emission wavelength of 470 nm, a light emission output of 3.0 mW, and a life test of about 5000 hours was performed. Results were obtained. Also, the variation in characteristics between elements was suppressed to 2% or less. It has been found that roughening the surface of the p-type GaN contact layer 306 improves the extraction efficiency due to light scattering and increases the light emission output.

Example 6
In this example, the LED characteristics when an n-type semiconductor substrate is a SiC substrate, a current blocking oxide film is formed below the pad electrode, and the n-type electrode is a transparent electrode will be described. FIG. 4 shows a cross-sectional view of a GaN-based compound semiconductor LED manufactured by the method of this example. As shown in FIG. 4, this LED has a buffer layer 407, an n-type GaN layer 403, a light emitting layer 404, a p-type cladding layer 405, a p-type contact layer 406, and a p-type electrode 411 in this order on an SiC substrate 402b. A protective film 413 made of SiO ₂ is formed on a part of the surface of the p-type contact layer 406, the side surface of the group III nitride semiconductor film, and a part of the side surface of the SiC substrate. In addition, an n-type electrode 421b, a current blocking layer 423, and a pad electrode 422 are formed on the light extraction surface side of the SiC substrate 402b. The protective film was formed on the end face of the groove after forming the groove 412 from the p-type contact layer 406 to the SiC substrate 402b. Hereinafter, a method for growing an LED made of a GaN-based compound semiconductor formed on a SiC substrate will be described.

The SiC substrate 402b (carrier concentration: 1 × 10 ¹⁷ cm ⁻³ ) was introduced into the MOCVD apparatus, and the temperature was raised to about 1050 ° C. while flowing N ₂ and NH ₃ each at 5 L / m. When the temperature rose, the carrier gas was changed from N ₂ to H ₂ , TMG 50 μmol / m, TMA 30 μmol / m, SiH ₄ 10 nmol / m were introduced, and an AlGaN film 407 buffer layer was grown to 50 nm. Subsequently, 100 μmol / m of TMG and 10 nmol / m of SiH ₄ were introduced to grow an n-type GaN layer 403 by about 4 μm. Thereafter, the supply of TMG was stopped, the carrier gas was changed from H ₂ to N ₂ again, the temperature was lowered to 700 ° C., and trimethylindium (TMI) as an indium raw material was introduced at 10 μmol / m, and TMG was introduced at 15 μmol / m. Then, a 4 nm thick barrier layer made of In _0.05 Ga _0.95 N was grown. Thereafter, the supply amount of TMI was increased to 50 μmol / m, and a 2 nm-thick well layer made of In _0.2 Ga _0.8 N was grown. The well layer is grown in a total of three layers in the same way, and a multiple quantum well (MQW) light emitting layer 404 is grown in which there are a total of four barrier layers between and on both sides of the well layer. did.

When the growth of MQW is finished, the supply of TMI and TMG is stopped, the temperature is raised again to 1050 ° C., the carrier gas is changed from N ₂ to H ₂ again, TMG is 50 μmol / m, TMA is 30 μmol / m, A p-type doping raw material, biscyclopentadienylmagnesium (Cp ₂ Mg), was flowed at 10 nmol / m to grow a 20 nm-thick p-type Al _0.2 Ga _0.8 N clad layer 405, and finally, supply of TMG Was adjusted to 100 μmol / m, the supply of TMA was stopped, and a 0.1 μm thick p-type GaN contact layer 406 was grown. When the growth was completed, the supply of TMG and Cp ₂ Mg was stopped, the temperature was lowered, and the film was taken out from the MOCVD apparatus at room temperature.

Next, a p-type electrode 411 was formed by the method shown in Example 1. Subsequently, a transparent and conductive tin oxide film (ITO film) 421b was formed on the entire surface of the SiC substrate 402b using a sputtering apparatus. The film thickness was 0.3 μm. Subsequently, a current blocking layer 423 made of silicon oxide (SiO ₂ ) was formed to a thickness of 0.1 μm on part of the ITO film 421b using a sputtering apparatus. Next, 3000 μg of Au was vapor-deposited on the current blocking layer 423 by vapor deposition to form an n-type electrode pad electrode 422. Thereafter, an LED was produced in the same manner as in Example 1.

  The LED manufactured in this example has an operating voltage of 3.0 V, a light emission wavelength of 470 nm, and a light emission output of 2.8 mW. A life test of about 5000 hours was carried out. Results were obtained. By observing the light emission pattern, it was found that the light emission directly under the pad electrode is reduced, the light extraction preventing action by the pad electrode can be reduced, the extraction efficiency is improved, and the light emission output is increased.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  According to the present invention, since the defect rate of light emitting elements can be reduced, gallium nitride compound semiconductors can be mass-produced on an industrial scale, and in particular, the market scale of light emitting diodes (LEDs) can be increased. it can.

1 is a schematic cross-sectional view showing the structure of a gallium nitride-based compound semiconductor light-emitting element of Example 1. FIG. 6 is a schematic cross-sectional view showing the structure of a gallium nitride-based compound semiconductor light-emitting element of Example 4. FIG. 6 is a schematic cross-sectional view showing the structure of a gallium nitride-based compound semiconductor light-emitting element of Example 5. FIG. 6 is a schematic cross-sectional view showing the structure of a gallium nitride-based compound semiconductor light-emitting element of Example 6. FIG.

Explanation of symbols

  2 GaN thick film substrate, 3 n-type GaN layer, 4 light emitting layer, 5 p-type cladding layer, 6 p-type contact layer, 11 p-type electrode, 12 groove, 13 protective film, 21 n-type electrode, 22 pad electrode.

Claims (13)

  A light-emitting element including a group III nitride semiconductor film and a p-type electrode on a light-transmitting n-type semiconductor substrate having conductivity, and extracting light from the n-type semiconductor substrate, the group III nitride semiconductor film A group III, comprising an insulating protective film on at least a part of the surface opposite to the light extraction direction, on a side surface of the group III nitride semiconductor film and on a side surface of the n-type semiconductor substrate Nitride semiconductor light emitting device.   2. The group III nitride according to claim 1, wherein the protective film on the side surface is formed in a region not less than 10 μm from the surface of the group III nitride semiconductor film and not more than the thickness of the n-type semiconductor substrate. Semiconductor light emitting device.   3. The group III nitride semiconductor light emitting device according to claim 1, wherein the side surface on which the protective film is formed is a side surface formed by etching or dicing of the group III nitride semiconductor film and the n-type semiconductor substrate.   The group III nitride semiconductor light-emitting device according to claim 1, wherein the n-type semiconductor substrate transmits light having a wavelength of 400 nm or more.   3. The group III nitride semiconductor light-emitting device according to claim 1, wherein the n-type semiconductor substrate is made of group III nitride or SiC. The group III nitride semiconductor light-emitting device according to claim 5, wherein the group III nitride semiconductor substrate has a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less. The group III nitride semiconductor light-emitting element according to claim 5, wherein the SiC semiconductor substrate has a carrier concentration of 5 × 10 ¹⁶ cm ⁻³ or more and 1 × 10 ¹⁸ cm ⁻³ or less.   The group III nitride semiconductor substrate is obtained by being formed on an underlying substrate by an epitaxial growth method and then removing a part or all of the underlying substrate by peeling, polishing, or etching. The group III nitride semiconductor light-emitting device according to claim 5.   2. The group III nitride semiconductor light-emitting device according to claim 1, wherein the n-type semiconductor substrate has a mesh-shaped n-type electrode and a pad electrode on a light extraction surface.   The group III nitride semiconductor light-emitting device according to claim 9, wherein the n-type electrode has translucency.   The group III nitride semiconductor light-emitting device according to claim 9, wherein the pad electrode has a current blocking structure at a portion in contact with the n-type electrode.   The group III nitride semiconductor light-emitting device according to claim 1, wherein the group III nitride semiconductor film has irregularities in a portion in contact with the p-type electrode.   The group III nitride semiconductor light-emitting device according to claim 12, wherein the irregularities have an arithmetic average roughness of 10 nm to 500 nm.

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