JP2003051613A - Gallium nitride based compound semiconductor and manufacturing method for element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve characteristics in p-type resistance reduction of a GaN- based compound semiconductor and in alloying of an electrode. SOLUTION: In a manufacturing method for a light-emitting element provided with an n<+> layer 13 of GaN, a clad layer 14 of n-type GaN, a light-emitting layer 15, a clad layer 16 of AlGaN to which Mg is added, a contact layer 17 of GaN to which Mg is added, a light-transmissive electrode 18A, and an electrode 18B; a surface of the n<+> layer 13 is exposed by etching a part of a layer provided on the upper side of the n<+> layer 13, the light transmissive electrode 18A is formed on the contact layer 17, the electrode 18B is formed on the exposed surface of the n<+> layer 13, heat treatment is conducted in the range of 500 to 600 deg.C inside a gas containing at least oxygen, and the p-type resistance reduction and an alloying processing are simultaneously performed. Satisfactory low resistance is obtained even at a low temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low resistance p-type gallium nitride compound semiconductor and a method of manufacturing an element having the semiconductor and an electrode.

[0002]

2. Description of the Related Art Conventionally, gallium nitride-based compound semiconductors are p-type.
Low resistance p-type conduction cannot be obtained only by adding a type impurity. Therefore, p-type impurities are added and then p-type resistance is reduced by utilizing electron beam irradiation (Japanese Patent Laid-Open No. 2-257679).
No.), p-type resistance by thermal annealing (Japanese Patent Laid-Open No. 5-183)
No. 189), and this thermal annealing for reducing the p-type resistance is performed in the same step as alloying at the time of forming electrodes (Japanese Patent Laid-Open No. 8-5123).
No. 5) is proposed.

[0003]

However, Japanese Unexamined Patent Publication No.
In the method by thermal annealing described in Japanese Patent No. 183189, as shown in FIG. 2, a practical temperature at which a saturated low resistance value is obtained needs to be 700 ° C. or higher. Aluminum has been mainly used for the electrode of this semiconductor for a long time, but when the electrode is alloyed at a temperature of 700 ° C. or higher, aluminum is melted and condensed into a ball shape, or the surface condition is deteriorated. This increases the contact resistance of the electrodes and causes wire bonding failure.

Therefore, the heat treatment for alloying the electrodes is
It needs to be performed at a relatively low temperature of 500 to 600 ° C. On the other hand, in the heat treatment for reducing the p-type resistance, a sufficiently low resistance value cannot be obtained in the range of 500 to 600 ° C. Therefore, it is necessary to separate the heat treatment step for reducing the p-type resistance and the heat treatment step for alloying the electrodes.

On the other hand, Japanese Unexamined Patent Publication No. 8-51235 proposes that heat treatment in the range of 400 to 800 ° C. simultaneously performs the treatment for lowering the p-type resistance and alloying the electrodes. However, in the low temperature region where the alloying of the electrode is favorably performed, the p-type resistance reduction is not sufficient, and p
In a high temperature region where the resistance of the die is sufficiently lowered, the electrodes are not well alloyed, and there are problems that the contact resistance becomes large and the ohmic property is not good.

Therefore, an object of the present invention is to realize a saturated low resistance value at a lower temperature in reducing the p-type resistance of a gallium nitride compound semiconductor. Another object is to realize p-type resistance reduction at a lower temperature, so that even if the heat treatment steps for p-type resistance reduction and electrode alloying are performed in the same step, sufficient p-type resistance reduction is achieved. It is to make it possible to obtain an electrode having a good ohmic property with a small resistance and contact resistance.

[0007]

According to a first aspect of the present invention, in a method for producing a p-type gallium nitride compound semiconductor, a p-type impurity-added gallium nitride compound semiconductor is heat-treated in a gas containing at least oxygen. It is characterized by doing. The second invention is a method of manufacturing an element having a p-type gallium nitride compound semiconductor layer and an electrode for the semiconductor layer, wherein a gallium nitride compound semiconductor layer to which a p-type impurity is added is formed and An electrode is formed on the gallium compound semiconductor layer, and the gallium nitride compound semiconductor layer having the electrode formed thereon is heat-treated in a gas containing at least oxygen. Further, a third invention is a method for manufacturing an element having a p-type gallium nitride compound semiconductor layer and an n-type gallium nitride compound semiconductor layer, wherein the gallium nitride compound semiconductor layer to which a p-type impurity is added is provided. One of the features is that after one electrode is formed and the second electrode is formed on the n-type gallium nitride-based compound semiconductor layer, heat treatment is performed in a gas containing at least oxygen. In addition, gallium nitride-based compound semiconductor is GaN
Is a compound in which a part of Ga is replaced with a Group 3 element such as In and Al. As an example, the general formula, (Al _x Ga _1-x ) _y In
It can be represented by a quaternary gallium nitride-based compound semiconductor of _1-y N (0 ≤ x ≤ 1,0 ≤ y ≤ 1).

In all the above inventions, the oxygen-containing gas may be at least one of O ₂ , O ₃ , CO, CO ₂ , NO, N ₂ O, NO ₂ or H ₂ O, or a combination thereof. Mixed gases can be used. Or, O ₂ , O ₃ , CO, CO ₂ , NO, N ₂ O,
NO ₂ or a mixed gas of at least one of H ₂ O and an inert gas, or a mixture of O ₂ , O ₃ , CO, CO ₂ , NO, N ₂ O, NO ₂ or H ₂ O A mixed gas of a gas and an inert gas can be used. In short, a gas containing oxygen is an oxygen atom,
It means a gas of a molecule having oxygen atoms.

The pressure of the atmosphere during the heat treatment may be higher than the pressure at which the gallium nitride compound semiconductor is not thermally decomposed at the heat treatment temperature. The gas containing oxygen, when using only O ₂ gas, may be introduced at a pressure equal to or higher than the decomposition pressure of the gallium nitride-based compound semiconductor, and when used in a state of being mixed with another inert gas, It suffices that all gases have a pressure not lower than the decomposition pressure of the gallium nitride-based compound semiconductor and that the O ₂ gas has a ratio of about 10 ⁻⁶ or more with respect to all gases.
In short, it is sufficient that the gas containing oxygen exists in an extremely small amount for the reason described below. The upper limit of the amount of the gas containing oxygen introduced is not particularly limited in view of the p-type resistance reduction and the electrode alloying characteristics. In short, it can be used to the extent that it can be manufactured.

Regarding heat treatment, most preferably,
It is 500-600 degreeC. As will be described later, it is possible to obtain a low-resistance p-type gallium nitride-based compound semiconductor whose resistivity is completely saturated at a temperature of 500 ° C. or higher. Also, 60
At a temperature of 0 ° C. or lower, the electrode alloying treatment can be favorably performed. Also, the desirable temperature range is 450 to 6
It is 50 degreeC, 400-600 degreeC, 400-700 degreeC.
The lower the temperature, the higher the p-type resistivity, and the higher the temperature, the worse the characteristics of the electrode and the more likely the crystal is thermally deteriorated.

The first electrode is preferably made of cobalt (Co) alloy, palladium (Pd), or palladium (Pd) alloy, and preferably has a metal layer having translucency and ohmic characteristics. In this case, the metal layer made of a cobalt (Co) alloy is a first metal layer made of cobalt (Co) and a second metal layer made of gold (Au) laminated on the first metal layer, Alternatively, a first metal layer made of gold (Au) and a second metal layer made of cobalt (Co) laminated on the first metal layer, or an alloy layer of cobalt (Co) and gold (Au) Is a layer alloyed by heat treatment. Alternatively, the metal layer made of a cobalt (Co) alloy includes a first metal layer made of cobalt (Co), a second metal layer made of a Group 2 element laminated on the first metal layer, The third metal layer made of gold (Au) laminated on the second metal layer is a layer alloyed by heat treatment. Further, the metal layer made of a palladium (Pd) alloy includes a first metal layer made of palladium (Pd) and a second metal layer made of gold (Au) laminated on the first metal layer, or A first metal layer made of gold (Au) and a second metal layer made of palladium (Pd) laminated on the first metal layer;
It is a layer alloyed by heat treatment. As the first electrode, the first metal layer made of nickel (Ni) and the gold (A
It is also possible that the second metal layer of u) is alloyed by heat treatment. The material of the first electrode is
It was selected from the viewpoint of improving the characteristics from the viewpoints of contact resistance to the p-type gallium nitride-based compound semiconductor, light emission pattern, aging of characteristics, junction strength, and ohmic characteristics.

The second electrode is aluminum (Al), or
It is preferably composed of an aluminum alloy. This is n
Type gallium nitride based compound semiconductor was selected in terms of contact resistance and ohmic contact.

[0013]

In the invention of claim 1, as a result of using the gas containing oxygen as the atmosphere gas for the heat treatment, the p-type low resistance gallium nitride compound semiconductor can be obtained at a lower temperature. As described later, it saturates at a temperature of 500 ° C. or higher in a low resistance value. Further, the resistance value tended to decrease from about 400 ° C., and at 450 ° C., the resistance value decreased to about a half of that at 400 ° C.

According to the second and third aspects of the present invention, at a lower temperature as described above, a saturation having a low resistance value that can be practically used can be obtained. Therefore, heat treatment for p-type conversion and alloying for electrodes are performed. The heat treatment can be performed in the same step.
As a result, the manufacturing process of the device is simplified. Further, as a result of heat treatment at a low temperature, thermal deterioration of the element is alleviated.

When heat treatment is performed in a gas containing oxygen,
The inventors of the present application considered the following as a reason for lowering the resistance at lower temperatures. That is, gallium nitride-based compound semiconductor
The reason why the p-type low resistance cannot be obtained only by adding the p-type impurity such as Mg is that the p-type impurity atom does not function as an acceptor because the p-type impurity atom and the hydrogen atom are bonded. Is being used. Therefore, it is considered that if the hydrogen atom bonded to the p-type impurity atom is taken out, it will function as an acceptor. Therefore, it is considered that by heat treatment in a gas containing oxygen, oxygen catalytically promotes dissociation with hydrogen atoms, and as a result, the resistivity decreases from a lower temperature.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on specific embodiments. The present invention is not limited to the examples below. Example of p-type low resistance method A large number of samples having the structure shown in FIG. 1 were prepared. The sample is a 50 nm AlN buffer layer 2 on a sapphire substrate 1,
Consists of silicon (Si) -doped GaN with a film thickness of about 4.0 μm, electron concentration of 2 × 10 ¹⁸ / cm ³ and silicon concentration of 4 × 10 ¹⁸ / cm ^3.
n-GnN layer 3, magnesium (Mg) concentration of 5 × 10 ¹⁹ / cm ³ p-
The GaN layer 4 is formed.

The method for manufacturing this sample is similar to the method for manufacturing a light emitting device described later, and is a metal organic chemical vapor deposition method (hereinafter MOV).
Manufactured by vapor phase epitaxy with PE). The gas used was ammonia (NH ₃ ), carrier gas (H ₂ , N ₂ ), trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”), trimethylaluminum (Al (CH ₃ ) ₃ ) (Hereinafter referred to as “TMA”), silane (SiH ₄ ), and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter referred to as “CP ₂ Mg”).

First, the single crystal sapphire substrate 1 whose main surface is the a-plane cleaned by organic cleaning and heat treatment is MOVP.
E Attach to the susceptor placed in the reaction chamber of the device. Next, the sapphire substrate 1 was baked at a temperature of 1100 ° C. while flowing H ₂ at a flow rate of ₂ liter / min into the reaction chamber at normal pressure for about 30 minutes.

Next, the temperature is lowered to 400 ° C. and H ₂
20 liter / min, NH ₃ 10 liter / min, TMA 1.8 ×
The buffer layer 2 made of AlN 3 was formed at a thickness of about 50 nm by supplying at 10 ⁻⁵ mol / min for about 1.5 minutes.

Next, the temperature of the sapphire substrate 1 is set to 1150.
Hold at ℃, H₂20 liter / min, NH ₃10 liter / min,
1.7 x 10 TMG^-FourMol / min, H₂0.86 by gas
20x10 silane diluted to ppm^-84 at mol / min
Supply for 0 minutes, film thickness about 4.0 μm, electron concentration 2 × 10¹⁸
/cm³, Silicon concentration 4 × 10¹⁸/cm³The n-GaN layer 3 of
did.

Next, the temperature of the sapphire substrate 1 is set to 1100.
℃ to retain, N ₂ or H ₂ 10liter / min, 10Lite the NH ₃
r / min, TMG 1.7 × 10 ^-4 mol / min, CP ₂ Mg 2 × 1
It is supplied at 0 ^-5 mol / min for 40 minutes to obtain a film thickness of about 4.0 μm,
A p-GaN layer 4 having a magnesium (Mg) concentration of 5 × 10 ¹⁹ / cm ³ was formed.

A large number of such samples were prepared, and heat treatment was carried out for 20 minutes at each temperature in an oxygen gas atmosphere at 1 atm (only O ₂ was present). At this time, a needle electrode was erected on the p-GaN layer 4 and the relationship between the current value flowing when a voltage of 8 V was applied and the heat treatment temperature was measured. On the other hand, as a comparative example,
As in the conventional case, the relationship between the current value and the heat treatment temperature was similarly measured for the sample that was similarly heat treated in a nitrogen gas atmosphere of 1 atm (only N ₂ was present). The resistance value was calculated, and the relationship between the heat treatment temperature and the resistance value is shown in FIG.

The following can be understood from FIG. 1) The resistance reduction rate (resistance value before heat treatment / resistance value after heat treatment) is 10 both in heat treatment in oxygen atmosphere and heat treatment in nitrogen atmosphere.
^{Is 4} . That is, there is no difference in the saturation value of the resistivity which decreases due to the heat treatment. 2) It is better to heat-treat in an oxygen atmosphere
As compared with the case of performing heat treatment in a nitrogen atmosphere, saturation of a low resistance value can be obtained from a lower temperature. 3) When the heat treatment is performed in an oxygen atmosphere, the change in resistivity with respect to the heat treatment temperature is more rapid than when heat treatment is performed in a nitrogen atmosphere. 4) Heat treatment in an oxygen atmosphere gives a low resistance saturation at 500 ° C., but heat treatment in a nitrogen atmosphere gives a saturation of 500.
The resistance change rate is about 10 at ℃. Therefore, 500
At ° C, the heat treatment in the oxygen atmosphere has a resistivity 10 ³ times smaller than that in the nitrogen atmosphere. 5) In the heat treatment at 400 ° C., there is almost no decrease in the resistivity in the oxygen atmosphere or the nitrogen atmosphere, and the decrease in the resistivity is seen in the heat treatment at that temperature or higher.

From the above, 400 in an oxygen atmosphere
The resistivity can be lowered by performing the heat treatment at a temperature of ℃ or more, and desirably, the saturation of the resistance value can be completely lowered by the heat treatment at a temperature of 500 ℃ or more.

Next, the relationship between the pressure of oxygen gas and the resistivity was measured. After the heat treatment was performed at a temperature of 800 ° C. under each pressure of oxygen gas, a needle electrode was erected on the p-GaN layer 4 and the relationship between the current value flowing when the voltage of 8 V was applied and the oxygen gas pressure was measured. As shown in FIG.

From the measurement results, the following can be understood.
1) When the oxygen gas pressure is in the range of about 3 to 30 Pa, the resistance value suddenly decreases. 2) Oxygen gas pressure is about 1
A saturation of a low resistance value can be obtained at 00 Pa or more.

From the above, it is understood that oxygen contributes to effectively lower the resistance value. If the oxygen gas pressure is 3 Pa or more, it is effective in reducing the resistivity, and is preferably 30 Pa or more, more preferably 100 Pa.

Next, the change characteristic of the resistance value with respect to the partial pressure of oxygen gas when heat-treated at a temperature of 600 ° C. in a mixed gas atmosphere of oxygen gas and nitrogen gas (1 atm) was measured in the same manner as described above. For comparison, the change characteristics of pressure and resistance when heat-treated only with oxygen gas were also measured. The result is shown in FIG. It can be seen that a low resistivity is obtained when the oxygen gas partial pressure is about 10 Pa or more. Again 3
At 0 Pa or more, completely at 100 Pa or more,
It can be seen that the resistance value is saturated. From this, when a mixed gas of oxygen gas and another gas is used, the partial pressure of oxygen gas, which is effective in reducing the resistance value, is 10 Pa or more, preferably 30 Pa or more, and more preferably 100 Pa or more.

For all the above properties, (Al _x Ga _1-x ) _y In
Mg in _1-y N (0 ≤ x, y ≤ 1) gallium nitride compound semiconductor
Similar results were obtained for layers doped with. Oxygen is taken to remove the H 2 atom bound to Mg and activate the Mg atom. Therefore, as long as it is a gas containing oxygen (0) atoms that can bond with H 2 atoms bonded to Mg, the same effect can be obtained with pure gas as well as other gases, for example, a mixed gas with an inert gas or the like.

Next, a method of manufacturing a light emitting device using the above p-type resistance lowering method will be described. FIG. 5 is a schematic structural sectional view of a light emitting device 100 formed of a GaN-based compound semiconductor formed on the sapphire substrate 1. A buffer layer 12 made of AlN is provided on a sapphire substrate 10, and a high carrier concentration n ⁺ layer 13 made of silicon (Si) -doped GaN is formed thereon. A cladding layer 14 made of silicon (Si) -doped n-type GaN is formed on the high carrier concentration n ⁺ layer 13.

Then, a thickness of 35Å is formed on the clad layer 14.
Barrier layer 151 made of GaN and In _0.20 Ga with a thickness of 35Å
A light emitting layer 5 having a multiple quantum well structure (MQW) composed of a well layer 152 of _0.80 N is formed. The barrier layer 151 has 6 layers and the well layer 152 has 5 layers. Light emitting layer 15
A clad layer 16 made of p-type Al _0.15 Ga _0.95 N is formed on the upper surface. Further, on the clad layer 16, p-type
A contact layer 17 made of GaN is formed.

On the contact layer 17, a light-transmitting electrode 18A formed by metal vapor deposition and on the n ⁺ layer 3 an electrode 18B.
Are formed. The translucent electrode 18A is composed of cobalt (Co) having a thickness of 40 Å which is bonded to the contact layer 17 and metal elements described later such as 60 Å gold (Au) which is bonded to the cobalt (Co). . The electrode 18B is composed of vanadium (V) having a thickness of 200Å and aluminum (Al) or an aluminum alloy having a thickness of 1.8 μm.

Next, a method of manufacturing the light emitting device 100 will be described. The light emitting device 100 was manufactured by vapor phase growth by a metal organic vapor phase epitaxy method (hereinafter, MOVPE). The gas used was ammonia (NH ₃ ), carrier gas (H ₂ , N ₂ ), TMG, TMA, trimethylindium (In (CH
₃ ) ₃ ) (hereinafter referred to as “TMI”), silane (SiH ₄ ) and CP ₂ Mg.

First, the MOV is performed on the single crystal sapphire substrate 10 whose main surface is the a-plane, which has been cleaned by organic cleaning and heat treatment.
It is attached to the susceptor placed in the reaction chamber of the PE device. Next, the sapphire substrate 10 was baked at a temperature of 1100 ° C. while flowing H ₂ into the reaction chamber at a flow rate of ₂ liter / min for about 30 minutes under normal pressure.

Next, the temperature is lowered to 400 ° C. and H _{2 is} added.
20 liter / min, NH ₃ 10 liter / min, TMA 1.8 ×
AlN buffer layer 1 supplied at 10 ^-5 mol / min for about 1 minute
2 was formed to a thickness of about 25 nm. Next, the temperature of the sapphire substrate 10 is maintained at 1150 ° C., and H ₂ is set to 20 liter /
Min, NH ₃ 10 liter / min, TMG 1.7 × 10 ^-4 mol / min
Silane diluted to 0.86 ppm with H ₂ gas at 20 × 10 ⁻⁸ mol / min for 40 minutes to obtain a film thickness of about 4.0.
μm, electron concentration 2 × 10 ¹⁸ / cm ³ , silicon concentration 4 × 10
^A high carrier concentration n ⁺ layer 13 composed of ¹⁸ / cm ³ GaN was formed.

Next, the temperature of the sapphire substrate 10 is set to 115.
Hold at 0 ℃, N₂Or H₂10 liter / min, NH₃10 li
ter / min, TMG 1.12 × 10^-FourMol / min, TMA of 0.
47 x 10^-FourMol / min, H₂0.86ppm by gas
5x10 diluted silane ^-9Supply for 60 minutes at mol / min
Then, the film thickness is about 0.5 μm and the electron concentration is 1 × 10.¹⁸/cm³, Shi
Recon concentration 2 × 10¹⁸/cm³Clad layer 1 of GaN
4 was formed.

After the cladding layer 14 is formed, N ₂ or H ₂ is added at 20 liter / min, NH ₃ is added at 10 liter / min, and TMG is added.
Was supplied at 2.0 × 10 ⁻⁴ mol / min for 1 minute to form a barrier layer 151 made of GaN with a film thickness of about 35 Å. Next, TMG was set to 7. with constant supply of N ₂ or H ₂ and NH ₃ .
2 × 10 ⁻⁵ mol / min and TMI of 0.19 × 10 ⁻⁴ mol / min were supplied for 1 minute to form a well layer 152 made of In _0.20 Ga _0.80 N with a film thickness of about 35 Å. Further, the barrier layer 151
And well layer 152 are formed under the same conditions for 5 periods, and Ga
A barrier layer 151 made of N 2 was formed. In this way, the light emitting layer 15 having the MQW structure of 5 cycles was formed.

Next, the temperature of the sapphire substrate 10 is set to 110.
Hold at 0 ℃, N₂Or H₂10 liter / min, NH₃10 li
ter / min, TMG 1.0 × 10^-FourMol / min, TMA 1.0
× 10^-FourMol / min, CP₂2 x 10 Mg^-Five3 minutes at mol / min
Supplying for 50nm, magnesium (Mg) concentration 5
× 10¹⁹/cm³P-type Al doped with magnesium (Mg)
_0.15Ga_0.85A cladding layer 71 made of N 2 was formed.

Next, the temperature of the sapphire substrate 10 is set to 110.
Held in 0 ° C., N ₂ or H ₂ 20liter / min, 10Li and NH ₃
ter / min, TMG 1.12 × 10 ⁻⁴ mol / min, CP ₂ Mg 2
A film thickness of about 100n is obtained by supplying it at × 10 ^-5 mol / min for 30 seconds.
m, a contact layer 17 made of p-type GaN doped with magnesium (Mg) having a magnesium (Mg) concentration of 5 × 10 ¹⁹ / cm ^3.
Was formed.

Next, an etching mask made of SiO ₂ is formed on the contact layer 17, the mask in a predetermined region is removed, and a portion of the contact layer 1 not covered with the mask is removed.
7, cladding layer 16, light emitting layer 15, cladding layer 14, n
A part of the ⁺ layer 13 was etched by reactive ion etching using a gas containing chlorine to expose the surface of the n ⁺ layer 13. Next, an electrode (second electrode) 18B for the n ⁺ layer 13 and a translucent electrode (first electrode) 18A for the contact layer 17 were formed by the following procedure.

(1) With the SiO ₂ mask left, a window is formed in a predetermined region by applying photoresist and photolithography, and a thickness of 20 is applied in a high vacuum of the order of 10 ⁻⁶ Torr or less.
0Å vanadium (V) and 1.8 μm thick aluminum
(Al) was deposited. Next, the photoresist and the SiO ₂ mask are removed. (2) Next, a photoresist 19 is uniformly applied on the surface, and the photoresist 19 on the electrode formation portion on the contact layer 17 is removed by photolithography, and the photoresist 19 shown in FIG.
The window portion 19A is formed as shown in FIG. (3) A first metal layer 81 made of cobalt (Co) is formed on the exposed contact layer 17 in a high vacuum of 10 ⁻⁶ Torr order or less by a vapor deposition apparatus, and then the first metal layer 81 is formed. A second metal layer 82 made of gold (Au) is formed on the first metal layer 81 by 60 Å. (4) Next, the sample is taken out from the vapor deposition apparatus, Co and Au deposited on the photoresist 19 are removed by the lift-off method, and the transparent electrode 18A for the contact layer 17 is formed. (5) Next, in order to form the electrode pad 20 for bonding on a part of the translucent electrode 18A, a photoresist is uniformly applied, and a window is formed on the photoresist in the portion where the electrode pad is formed. Open. Next, cobalt (Co) or nickel (Ni) and gold (Au), aluminum (Al), or an alloy thereof is formed to a film thickness of about 1.5 μm by vapor deposition,
Similar to the step (4), the electrode pad 20 is removed by the lift-off method to remove the film made of Co or Ni and Au, Al, or an alloy thereof deposited by vapor deposition on the photoresist.
To form. (7) After that, the sample atmosphere was evacuated by a vacuum pump, O ₂ gas was supplied to make the pressure 100 Pa, and in that state, the atmosphere temperature was set to about 550 ° C. and heated for about 3 minutes.
7. The p-type resistance of the clad layer 16 was reduced, and the contact layer 17, the first metal layer 81, and the second metal layer 82 were alloyed, and the electrode 18B and the n ⁺ layer 13 were alloyed.

By this heat treatment, the specific resistance of the contact layer 17 is 1 Ωcm and the specific resistance of the cladding layer 16 is 0.71 Ωcm.
Became. This heat treatment is most preferably in the range of 500 to 600 ° C. Within the temperature range, the p-type layer is in a saturation region where the resistance value is sufficiently low, and the electrodes 18A and 1
The alloying in 8B is performed in the highest quality, the contact resistance of the electrode is reduced, the ohmic property is improved, the translucent electrode 18A is prevented from being oxidized, and the light emission pattern is not uneven, and the light emission pattern does not change over time. can do. It should be noted that the heat treatment causes a slight deterioration in the characteristics, but 450 to
It can be used at 650 ° C, and in some cases, it can be performed in the range of 400 to 700 ° C. From the viewpoint of alloying treatment of the electrode, the electrode does not show ohmic characteristics when heat-treated at less than 400 ° C, and the p-type layer still shows sufficiently low resistance value when heat-treated at a temperature higher than 700 ° C. However, the contact resistance of the electrode increases and the surface morphology deteriorates,
It may also be a cause of defective wire bonding in a later step. Therefore, it is desirable to perform heat treatment within the range of 400 ° C to 700 ° C.

A heat treatment was performed in an atmosphere in which 1% O ₂ gas was contained in N ₂ gas and the partial pressure of the O ₂ gas was 100 Pa, but the same effect was obtained. Further, the atmosphere gas of the heat treatment described in the p-type resistance lowering method effectively acts as it is in alloying the electrodes 18A and 18B. Therefore, other pure oxygen gas, the _{O 2 N 2, He, Ne} , Ar, Kr
One or more of the above gases can be used, and the pressure and the partial pressure of O ₂ can all be used within the optimum range for the p-type resistance reduction described above.

After the cobalt (Co) and the gold (Au) are laminated, the above heat treatment results, and as a result, the first metal layer 8 made of cobalt (Co) 8 is formed.
The gold (Au) of the second metal layer 82 above the first metal layer 81 is diffused into the contact layer 17 through the first metal layer 81.
It forms an alloy state with GaN of No. 7.

The light emitting device 100 thus formed
On the other hand, when a current of 20 mA was applied, a driving voltage of 3.5 V was obtained, and it was confirmed that the contact resistance was sufficiently small. or,
The transparent electrode 18A was uniformly formed on the entire surface of the contact layer 17, and a good surface condition was obtained. Further, in the translucent electrode 18A, since the second metal layer 82 is laminated on the first metal layer 81 made of cobalt (Co), the oxidation of cobalt (Co) is prevented and the oxidation of cobalt (Co) is caused. It is possible to prevent a change in the light emitting pattern, a decrease in translucency, and an increase in contact resistance. Further, since the transparent electrode 18A is an alloy containing cobalt (Co) having a large work function, good ohmic characteristics can be obtained. When the electrode 18A was subjected to a aging test under a high temperature and high humidity atmosphere, the initial light emission pattern and the driving voltage could be stably maintained even after 1000 hours had elapsed.

In addition, the transparent electrode 18A can be combined with other various materials. For example, the first metal layer 81 may be gold (Au) having a thickness of 40 Å, and the second metal layer 82 may be cobalt (Co) having a thickness of 60 Å. Also, 100 Å thick cobalt
Only the first metal layer 81 made of an alloy of (Co) and gold (Au) may be formed. Further, a first metal layer 81 made of cobalt (Co) having a thickness of 20Å is formed, a second metal layer 82 made of magnesium (Mg) having a thickness of 20Å is formed on the first metal layer 81, and a second metal layer 82 having a thickness of 60Å is formed thereon. It is also possible to form a third metal layer made of gold (Au) and form the transparent electrode in a three-layer structure. The light emitting device 100 having the translucent electrode 18A having these structures was heat-treated at the above-mentioned temperature and atmospheric gas. Similar results were obtained when a current of 20 mA was applied to the transparent electrode 18A.

Further, all the above light emitting devices 100 were subjected to a continuous driving test for 1000 hours in a high temperature and high humidity atmosphere. After 1000 hours, the driving voltage did not change and the light emission pattern did not change, and stable characteristics were obtained over time, both optically and electrically.

The magnesium (Mg) in the above metal layer is
Instead of this, beryllium (Be), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), cadmium
A Group 2 element such as (Cd) may be used.

In addition, the translucent electrode 18A is made of palladium (P
It may be composed of d) and a gold (Au) alloy. As the first metal layer 81, palladium (Pd) having a film thickness of 40 Å is formed on the contact layer 17, and the second metal layer 82 made of gold (Au) having a film thickness of 60 Å is formed on the first metal layer 81. By performing the alloying treatment under the above-mentioned conditions, a stable light emission pattern over time and a low driving voltage of less than 4 V were obtained. Translucent electrode 18A
Is an alloy of palladium (Pd) having a high work function, so that good ohmic characteristics were obtained.

As the first metal layer 81, gold (A
u) is formed on the contact layer 17 and the first metal layer 81 thereof is formed.
A second metal layer 82 made of palladium (Pd) with a film thickness of 60 Å on top
Was formed and the alloying treatment was performed under the above-mentioned conditions, a stable light emission pattern with time and a low driving voltage of less than 4 v were obtained. Further, after 1000 hours, there was no change in the driving voltage, no change in the light emission pattern was observed, and stable characteristics were obtained both optically and over time.

Further, in the above embodiment, the transparent electrode 18
As for A, Ni and Au may be laminated and alloyed under the above conditions.
Also in this case, the driving voltage of the electrodes was less than 4 V, and a light emitting element having a good light emitting pattern was obtained.

Although the light emitting layer 15 of the light emitting device 100 has the MQW structure, it may be a single layer made of SQW, In _0.2 Ga _0.8 N, or the like, or any other mixed crystal quaternary or ternary AlInGaN. Also, Mg was used as the p-type impurity, but beryllium (B
Group 4 elements such as e) and zinc (Zn) can be used.

Although the above embodiments have been described with respect to a light emitting diode having a transparent electrode, the present invention is applicable to a high temperature device and a power source which are expected to develop a laser diode (LD), a light receiving element, and other gallium nitride compound semiconductor elements. It can also be applied to electronic devices such as devices.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a sample according to a p-type resistance lowering method of the present invention.

FIG. 2 is a characteristic diagram showing characteristics of resistance change with respect to a heat treatment temperature of a sample obtained by the p-type resistance lowering method of the present invention.

FIG. 3 is a characteristic diagram showing characteristics of resistance change with respect to oxygen gas pressure during heat treatment of a sample obtained by the p-type resistance lowering method of the present invention.

FIG. 4 is a characteristic diagram comparing the characteristic of resistance change with respect to oxygen gas partial pressure of the sample obtained by the p-type resistance lowering method of the present invention with the characteristic of resistance change of a sample heat-treated in a pure oxygen gas atmosphere. .

FIG. 5 is a cross-sectional view showing a configuration of a light emitting device according to a manufacturing method of the present invention.

FIG. 6 is a cross-sectional view showing a method of forming electrodes of a light emitting element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sapphire substrate 2 ... Buffer layer 3 ... N ⁺ layer 4 ... P layer 10 ... Sapphire substrate 12 ... Buffer layer 13 ... N ⁺ layer 14 ... Clad layer 15 ... Emitting layer 16 ... Clad layer 17 ... Contact layers 18A, 18B ... Electrode 19A ... Window 81 ... First metal layer 82 ... Second metal layer 100 ... Light emitting element

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jun Ito             Aichi Prefecture Kasuga-cho, Nishikasugai-gun Ochiai character Nagahata 1             Address within Toyoda Gosei Co., Ltd. F-term (reference) 4M104 AA04 BB02 BB04 BB05 BB07                       BB09 BB13 BB36 CC01 DD16                       DD34 DD68 DD71 DD78 DD83                       DD92 FF03 GG04 GG05 GG18                       HH15                 5F041 AA08 AA24 CA05 CA40 CA49                       CA53 CA57 CA73 CA85 CA92                       CA99

Claims (5)

[Claims] 1. A method for producing a p-type gallium nitride compound semiconductor, wherein the gallium nitride compound semiconductor to which a p-type impurity is added is heat-treated in a gas containing at least oxygen. Semiconductor manufacturing method. 2. A method for manufacturing an element having a p-type gallium nitride compound semiconductor layer and an electrode, wherein a gallium nitride compound semiconductor layer to which a p-type impurity is added is formed, and the gallium nitride compound semiconductor layer is formed. A method for producing a gallium nitride-based compound semiconductor device, comprising forming an electrode, and heat-treating the gallium nitride-based compound semiconductor layer having the electrode formed therein, in a gas containing at least oxygen. 3. A p-type gallium nitride-based compound semiconductor layer, and n
In a method of manufacturing an element having a gallium nitride-based compound semiconductor layer and electrodes for the respective layers, a first electrode is formed on the p-type impurity-added gallium nitride-based compound semiconductor layer, and the n-type gallium nitride-based compound is formed. A method for manufacturing a gallium nitride-based compound semiconductor device, which comprises performing a heat treatment in a gas containing at least oxygen after forming the second electrode on the semiconductor layer. 4. The gas containing oxygen is O ₂ , O ₃ , CO or C.
At least one of O ₂ , NO, N ₂ O, NO ₂ , or H ₂ O, or a mixed gas thereof, or a mixed gas of these gases and an inert gas. The manufacturing method according to claim 3. 5. The heat treatment according to claim 1, wherein the heat treatment is performed at a temperature of 400 ° C. or higher.
The manufacturing method according to item.