JPH10178211A - Method for changing conductivity type of gallium nitride base compound semiconductor to p-type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the conductivity type of a gallium nitride base compound semiconductor doped with p-type impurities to a low-resistivity p-type and to ensure a uniform resistivity of the p-type gallium nitride compound semiconductor on the whole wafer. SOLUTION: A method for changing the conductivity type of a gallium nitride compound semiconductor to p-type comprises a step of growing a buffer layer by vapor deposition on a substrate, a step of growing a gallium nitride compound semiconductor layer containing p-type impurities on a wafer on which the buffer layer is grown and a step of annealing the buffer layer and the wafer on which the gallium nitride compound semiconductor layer is grown to change the conductivity type of the gallium nitride compound semiconductor layer containing p-type impurities to p-type. If the annealing time is set to 10min., the resistivity of the GaN layer doped with Mg starts decreasing suddenly at a temperature exceeding 400 deg.C and a constantly low resistivity as p-type characteristic is exhibited at 700 deg.C and higher, which is an effect of annealing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride-based compound semiconductor for use in light-emitting devices such as ultraviolet and blue light-emitting laser diodes, ultraviolet and blue light-emitting diodes, and more particularly to gallium nitride doped with p-type impurities. The present invention relates to a method for converting a p-type compound semiconductor.

[0002]

2. Description of the Related Art A blue light emitting device is a ZnS of II-VI group.
e, studies using SiC of the IV-IV group, GaN of the III-V group, etc., have recently been conducted, and among them, gallium nitride-based compound semiconductors [In _x Al _Y Ga _{1- x Y} N (0 ≦ X, 0 ≦
Y, X + Y ≦ 1)] have been reported to exhibit relatively excellent luminescence at room temperature, and have attracted attention. The blue light-emitting device having the nitride semiconductor is basically formed on a substrate made of sapphire by a general formula of In _x Al _Y Ga _{1 -XYN} (0 ≦ X, 0 ≦
Y, X + Y ≦ 1) has a structure in which epitaxial layers of a nitride semiconductor represented by the following formula are stacked in order of n-type and i-type or p-type.

As a method of laminating a nitride semiconductor, a metal organic compound vapor deposition method (hereinafter referred to as MOCVD method),
Vapor phase growth methods such as molecular beam epitaxy (hereinafter referred to as MBE) are well known. For example, the method using the MOCVD method will be briefly described. In this method, an organometallic compound gas such as trimethylgallium (TMG), trimethylaluminum (TMA), ammonia or the like is used as a reaction gas in a reaction vessel provided with a sapphire substrate. Is supplied, the crystal growth temperature is maintained at a high temperature of about 900 ° C. to 1100 ° C., and the nitride semiconductor is grown on the substrate. , I-type, or p-type.
In addition to sapphire, the substrate may be SiC, Si, or the like, but sapphire is generally used. Well-known n-type impurities are Si, Ge, and Sn (however, in the case of a nitride semiconductor, they have a property of becoming n-type without doping with an n-type impurity). Cd, B
e, Mg, Ca, Ba and the like.
g and Zn are best known.

Further, as one method of forming a nitride semiconductor by the MOCVD method, if a nitride semiconductor is grown directly on a sapphire substrate at a high temperature, the surface state and crystallinity are significantly deteriorated. Before you do,
Forming a buffer layer made of AlN at a low temperature of about 0 ° C.,
Subsequently, it has been revealed that the crystallinity is remarkably improved by performing growth at a high temperature on the buffer layer (Japanese Patent Application Laid-Open No. 2-229476).

However, a blue light emitting device having a nitride semiconductor has not yet been put to practical use. This is because a nitride semiconductor cannot be made into a p-type with low resistance, so that a light-emitting element having various structures such as a double hetero structure and a single hetero structure cannot be formed. Even if a nitride semiconductor doped with a p-type impurity is grown by a vapor phase growth method, the obtained nitride semiconductor does not become p-type and a high-resistance semi-insulating material having a resistivity of 10 ⁸ Ω · cm or more. That is, it was the actual situation that it became i-type. For this reason, at present, only the so-called MIS structure of a blue light emitting element is known, in which a buffer layer, an n-type layer, and an i-type layer are sequentially stacked on a substrate.

[0006]

As means for lowering the resistance of a high-resistance i-type so as to approach the p-type, Japanese Patent Laid-Open No. 2-25 / 1990
No. 7679, a high-resistance i-type gallium nitride compound semiconductor doped with Mg as a p-type impurity is formed in the uppermost layer, and then the surface is irradiated with an electron beam having an accelerating voltage of 6 kV to 30 kV so that about 0.5 μm
A technique for reducing the resistance of a layer has been disclosed. However, this method has a problem that only the penetration depth of the electron beam, that is, the resistance can be reduced only on the very surface, and the entire wafer must be irradiated while scanning the electron beam, so that the resistance cannot be reduced uniformly in the plane. there were.

Accordingly, an object of the present invention is to make a nitride semiconductor doped with a p-type impurity a low-resistance p-type, and furthermore to make the resistance of the p-type gallium nitride-based compound semiconductor uniform over the entire wafer. Gallium compound semiconductor
It provides a way to type.

[0008]

According to the present invention, there is provided a method for converting a gallium nitride-based compound semiconductor to a p-type by a vapor phase growth method, comprising the steps of: growing a buffer layer on the surface of a substrate; Growing a gallium nitride-based compound semiconductor layer doped with a p-type impurity on the wafer;
Annealing the wafer on which the buffer layer and the gallium nitride-based compound semiconductor layer have been grown to convert the gallium nitride-based compound semiconductor layer containing p-type impurities into p-type.

Further, in the method for converting a gallium nitride-based compound semiconductor to a p-type according to the second aspect of the present invention, the buffer layer is a GaN layer.

Further, according to a third aspect of the present invention, in the method for converting a gallium nitride-based compound semiconductor to a p-type, the substrate includes a buffer layer, an n-type gallium nitride-based compound semiconductor layer, and a p-type impurity. The wafer on which the gallium nitride-based compound semiconductor layer is grown is annealed to convert the gallium nitride-based compound semiconductor containing p-type impurities into p-type.

Annealing (Annealing: annealing,
The heat treatment) may be performed in a reaction vessel after growing a gallium nitride-based compound semiconductor layer doped with a p-type impurity, or may be performed using an apparatus dedicated to annealing after removing the wafer from the reaction vessel. The annealing atmosphere is performed in a vacuum, in an atmosphere of an inert gas such as N ₂ , He, Ne, or Ar, or in a mixed gas atmosphere thereof. Preferably, nitrogen is pressurized at a temperature higher than the decomposition pressure of the gallium nitride-based compound semiconductor at the annealing temperature. Perform in an atmosphere. This is because pressurization in a nitrogen atmosphere has an effect of preventing N in the gallium nitride-based compound semiconductor from decomposing and coming out during annealing.

For example, in the case of GaN, the decomposition pressure of GaN is 8
About 0.01 atm at 00 ° C, about 1 atm at 1000 ° C, 11
It is about 10 atmospheres at 00 ° C. Therefore, when annealing a gallium nitride-based compound semiconductor at 400 ° C. or higher,
More or less decomposition of the gallium nitride-based compound semiconductor occurs, and its crystallinity tends to deteriorate. Accordingly, decomposition can be prevented by pressurizing with nitrogen as described above.

The annealing temperature is, for example, 400 ° C.
The above is carried out at preferably 700 ° C. or more, for 1 minute or more, preferably for 10 minutes or more. Even at a temperature of 1000 ° C. or higher, decomposition can be prevented by pressurizing with nitrogen as described above, and as described later, a stable p-type gallium nitride-based compound semiconductor having excellent crystallinity can be obtained. .

As a means for suppressing the decomposition of the gallium nitride-based compound semiconductor during the annealing, a cap layer may be further formed on the gallium nitride-based compound semiconductor layer doped with a p-type impurity, followed by annealing. Good. The cap layer is a protective film, which is formed on a gallium nitride-based compound semiconductor doped with a p-type impurity, and then annealed at 400 ° C. or more to reduce the pressure, not to mention the pressure. Even under normal pressure, the gallium nitride-based compound semiconductor can be made into a low-resistance p-type without decomposing.

In order to form a cap layer, a gallium nitride-based compound semiconductor layer doped with a p-type impurity may be formed and then formed in a reaction vessel, or a wafer may be taken out of the reaction vessel. It may be formed by another crystal growth apparatus such as a plasma CVD apparatus. As the material of the cap layer, any material can be used as long as it is a material that can be formed on a gallium nitride-based compound semiconductor and is stable at 400 ° C. or higher, and preferably Ga _x Al ₁ -XN (where 0 ≦ X ≦ 1), Si ₃ N ₄ , and SiO _2, and the type of material is appropriately selected depending on the annealing temperature. The cap layer is usually formed with a thickness of 0.01 to 5 μm. When the thickness is less than 0.01 μm, the effect as a protective film cannot be sufficiently obtained. When the thickness is more than 5 μm, it takes time to remove the cap layer by etching after annealing and expose the p-type gallium nitride-based compound semiconductor layer. This is not economical.

[0016]

FIG. 1 is a diagram showing that a gallium nitride-based compound semiconductor layer doped with a p-type impurity changes to a low-resistance p-type by annealing. However, this figure shows the MO
First, a GaN buffer layer is formed on a sapphire substrate using a CVD method, and a GaN layer is formed to a thickness of 4 μm while doping Mg as a p-type impurity thereon. Then, the wafer is taken out and the temperature is changed. FIG. 3 is a diagram in which holes are measured on a wafer after annealing is performed for 10 minutes in a nitrogen atmosphere, and resistivity is plotted as a function of annealing temperature.

As can be seen from this figure, when the annealing time is set to 10 minutes, the resistivity of the Mg-doped GaN layer rapidly decreases from around 400 ° C.
It shows almost constant low-resistance P-type characteristics from 00 ° C.
The effect of annealing appears. The GaN layer not annealed and the Ga annealed at 700 ° C. or more
The hole measurement results of the N layer show that the GaN layer before annealing has a resistivity of 2 × 10 ⁵ Ω · cm and a hole carrier concentration of 8 × 1.
0 ¹⁰ / cm ³ , whereas Ga after annealing
The N layer has a resistivity of 2Ω · cm and a hole carrier concentration of 2 × 10
¹⁷ / cm ³ .

Further, the 4 μm GaN layer annealed at 700 ° C. is etched to a thickness of 2 μm,
As a result of the hole measurement, a hole carrier concentration of 2 × 10
¹⁷ / cm ³ and resistivity ³ Ω · cm, which were almost the same values as before etching. That is, the GaN layer doped with the P-type impurity becomes low-resistance p-type uniformly in the depth direction over the entire region by annealing.

FIG. 2 shows a wafer obtained by forming a GaN buffer layer and a Mg-doped GaN layer of 4 μm on a sapphire substrate by MOCVD.
Annealing was performed for 20 minutes in a nitrogen atmosphere at 000 ° C., and the p-type GaN layers of the wafer (a) performed under a pressure of 20 atm and the wafer (b) performed at an atmospheric pressure were respectively subjected to H annealing.
FIG. 3 is a diagram illustrating irradiation with an e-Cd laser as an excitation light source, and comparison of crystallinity with photoluminescence intensity thereof.
The higher the blue luminescence intensity of the photoluminescence at 450 nm, the better the crystallinity can be evaluated.

As shown in FIG. 2, when annealing is performed at a high temperature of 1000 ° C. or higher, the crystallinity of the GaN layer tends to be degraded due to the thermal decomposition. P-type G with excellent crystallinity
An aN layer is obtained.

FIG. 3 shows a wafer (c) in which a GaN buffer layer and a 4 μm Mg-doped GaN layer are formed on a sapphire substrate, and a 0.5 μm AlN layer as a cap layer thereon. The wafer (d) grown at a thick thickness is then subjected to a pressure of 1000
After annealing for 20 minutes in a nitrogen atmosphere at ℃
P exposed by removing the cap layer by etching
FIG. 4 is a diagram showing the crystallinity of a GaN layer in comparison with the photoluminescence intensity.

As shown in FIG. 3, the p-type GaN layer (c) annealed without growing the cap layer is decomposed when the annealing is performed at a high temperature. Becomes weaker. However, by growing the cap layer (in this case, AlN), the AlN of the cap layer is decomposed but the p-type GaN layer is not decomposed, so that the emission intensity is still strong.

The reason why a low-resistance p-type gallium nitride-based compound semiconductor can be obtained by annealing is presumed to be as follows.

That is, in growing a gallium nitride based compound semiconductor layer, NH ₃ is generally used as an N source, and it is considered that this NH ₃ is decomposed during growth to form atomic hydrogen. It is considered that this atomic hydrogen combines with Mg, Zn, or the like doped as an acceptor impurity to prevent p-type impurities, such as Mg or Zn, from functioning as an acceptor. For this reason, p
A gallium nitride-based compound semiconductor doped with a type impurity exhibits high resistance.

However, by performing annealing after the growth, hydrogen bonded in the form of Mg—H, Zn—H or the like is thermally dissociated, and the gallium nitride-based compound semiconductor layer doped with p-type impurities is removed. Since the p-type impurity comes out and functions normally as an acceptor, a low-resistance p-type impurity
A gallium nitride-based compound semiconductor can be obtained. Therefore, it is not preferable to use a gas containing a hydrogen atom such as NH ₃ or H ₂ in the annealing atmosphere. It is not preferable to use a material containing a hydrogen atom also in the cap layer for the above-described reason. In the present invention,
The hydrogen removed from the gallium nitride-based compound semiconductor containing the p-type impurity does not necessarily mean that all of the hydrogen is removed, and that some of the hydrogen is removed is within the scope of the present invention. Needless to say.

Further, in the method of converting a gallium nitride compound semiconductor into a p-type according to the present invention, a gallium nitride compound semiconductor layer containing a p-type impurity is grown on a substrate via a buffer layer. Due to the buffer layer, the crystallinity of the gallium nitride-based compound semiconductor layer containing a p-type impurity is extremely improved. When a gallium nitride-based compound semiconductor layer containing a p-type impurity having excellent crystallinity is annealed, Mg-H,
Hydrogen is dissociated and removed from the p-type impurity bonded in the form of Zn-H or the like. In this state, the p-type impurity becomes
In a gallium nitride based compound semiconductor layer with good crystallinity,
It normally works as an acceptor, and becomes a p-type gallium nitride-based compound semiconductor having lower resistance.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. [Example 1] First, a well-cleaned sapphire substrate is placed on a susceptor in a reaction vessel. After evacuating the container, the substrate is heated at 1050 ° C. for 20 minutes while flowing hydrogen gas to remove oxides on the surface. Then, the temperature is set to 5
After cooling to 10 ° C., at 510 ° C.
The GaN buffer layer was formed to a thickness of 200 Å while flowing the MG gas at 27 × 10 ⁻⁶ mol / min, the ammonia gas at 4.0 L / min as the N source, and the hydrogen gas at 2.0 L / min as the carrier gas. Grow with.

Next, only the TMG gas was stopped and the temperature was increased to 103.
After the temperature was raised to 0 ° C., TMG gas was again supplied to 54 × 10 ^−6.
Mol / min, a new Cp ₂ Mg (cyclopentadienyl magnesium) gas was flowed at 3.6 × 10 ⁻⁶ mol / min for 60 minutes to grow the Mg-doped GaN layer into 4 g / m 2.
It is grown to a thickness of μm.

After cooling, the wafer grown above was taken out of the reaction vessel, placed in an annealing apparatus, and annealed at 800 ° C. for 20 minutes in a nitrogen atmosphere at normal pressure.

As a result of hole measurement of the p-type GaN layer obtained by annealing, excellent p-type characteristics such as a resistivity of 2 Ω · cm and a hole carrier concentration of 2 × 10 ¹⁷ / cm ³ were exhibited.

Example 2 In Example 1, after growing the Mg-doped GaN layer, the Cp ₂ Mg gas was stopped, and then the GaN layer was grown to a thickness of 0.5 μm as a cap layer.

In the same manner as in Example 1, the annealing apparatus was used under a normal pressure under a mixed gas atmosphere of nitrogen and argon.
Anneal at 0 ° C. for 20 minutes. Thereafter, the layer of 0.5 μm was removed from the surface by dry etching,
The cap layer was removed to expose the p-type GaN layer, and a hole measurement was performed in the same manner. As a result, excellent p-type characteristics such as a resistivity of 2 Ω · cm and a carrier concentration of 1.5 × 10 ¹⁷ / cm ³ were exhibited. Note that the photoluminescence blue light emission intensity at 450 nm was about four times stronger than that of Example 1.

Example 3 In Example 1, after the Mg-doped GaN layer was grown, the wafer was taken out of the reaction vessel, and annealed in a nitrogen atmosphere at 20 ° C. and 800 ° C. for 20 minutes. As a result of the Hall measurement, excellent p-type characteristics such as a resistivity of 2 Ω · cm and a carrier concentration of 2.0 × 10 ¹⁷ / cm ³ were obtained, and the emission intensity of photoluminescence at 450 nm was measured in Example 1.
Was about four times stronger than

Example 4 In Example 1, after the Mg-doped GaN layer was grown, the wafer was taken out of the reaction vessel, and a plasma CVD apparatus was used. A 0.5 μm SiO ₂ layer was formed thereon as a cap layer. It is formed with a film thickness.

In an annealing apparatus, a nitrogen atmosphere,
Anneal at atmospheric pressure at 1000 ° C. for 20 minutes.
Thereafter, the SiO ₂ cap layer was removed with hydrofluoric acid, and the p-type GaN layer was exposed.
Resistivity 2Ω · cm, carrier concentration 2.0 × 10 ^I7 / cm
^It showed excellent p-type characteristics of ³ . The emission intensity of photoluminescence at 450 nm is about 20 times lower than that obtained by annealing under the same conditions without forming a cap layer.
It was twice as strong.

Example 5 In Example 1, after growing the Mg-doped GaN layer, the Cp ₂ Mg gas was stopped and TMA gas was newly added at 6 × 10 ⁻⁶ mol / min and Si was added.
2.2 × 10 ⁻¹⁰ mol / min of H ₄ (monosilane) gas
Flow for 0 minutes, n-type Ga _0.9 Al _0.1 doped with Si
An N layer is grown to a thickness of 0.8 μm.

After stopping TMG gas, TMA gas and SiH ₄ gas and cooling to room temperature while flowing hydrogen gas and ammonia gas, the wafer is taken out, put into an annealing apparatus, and held at 700 ° C. for 20 minutes in a nitrogen atmosphere. And perform annealing.

In this manner, the p-type G
An element having a single hetero structure in which an aN layer and an n-type Ga _0.9 Al _0.1 N layer were sequentially stacked was obtained. The gallium nitride-based compound semiconductor layer of this device was formed by n-type Ga _0.9 Al _0.1
A part of the N layer was etched to expose a part of the p-type GaN layer, an ohmic electrode was attached to each layer, and then cut into chips using a dicing saw. Electrodes were removed from the exposed n-type layer and p-type layer, and then molded to produce a blue light emitting diode. The characteristics of this light emitting diode are as follows.
It emitted blue light of 0 μW and had a peak wavelength of 430 nm. This light emission output is a high value which has not been reported in the past as the output of the blue light emitting diode.

On the other hand, when a light emitting diode having the same single heterostructure was manufactured without annealing, the light emitting diode had a forward voltage of about 60 V at a forward current of 20 mA, and the light emission was slightly yellow. It only glowed in color and was immediately broken, and the luminescence output could not be measured.

Embodiment 6 A GaN buffer layer having a thickness of 200 Å is formed on a sapphire substrate in the same manner as in Embodiment 1.

Next, only the TMG gas was stopped, and the temperature was changed to 103.
After the temperature was raised to 0 ° C., TMG gas was
^-6 mol / min and a new SiH ₄ (monosilane) gas flowing at 2.2 × 10 ⁻¹⁰ mol / min for 60 minutes to grow the Si-doped n-type GaN layer to a thickness of 4 μm. grow up.

Subsequently, the SiH ₄ gas is stopped, and the Cp ₂ Mg gas is grown at a flow ^rate of 3.6 × 10 ⁻⁶ mol / min for 30 minutes to grow the Mg-doped GaN layer to a thickness of 2.0 μm.

After stopping the TMG gas and the Cp ₂ Mg gas and cooling to room temperature while flowing hydrogen gas and ammonia gas, the gas flowing in the reaction vessel is replaced with nitrogen gas, and the gas in the reaction vessel is cooled while flowing nitrogen gas. The temperature is raised to 1000 ° C. and held in the reaction vessel for 20 minutes for annealing.

When the device thus obtained was used as a light emitting diode and emitted light, the device exhibited blue light emission having an emission peak near 430 nm and an emission output of 50 μm at 20 mA.
W, and the forward voltage was also 4 V at 20 mA. In addition, when a device having the same structure was produced without annealing and used as a light emitting diode, the light emitting device emitted a slightly yellow light at 20 mA, and the diode was immediately broken.

[0045]

The method for converting a gallium nitride-based compound semiconductor into a p-type semiconductor according to the present invention realizes the following excellent features. Until now, even if a p-type impurity is doped, a low resistance p
A gallium nitride-based compound semiconductor that has been extremely difficult to form as a mold layer can be annealed to form a low-resistance p-type gallium nitride-based compound semiconductor. In particular, the method for converting a gallium nitride-based compound semiconductor to a p-type according to the present invention uses a gallium nitride-based compound semiconductor containing a p-type impurity as a p-type by a very simple method of annealing. Gallium nitride based compound semiconductor
It has the feature that mass production of light emitting devices and the like is possible. Gallium nitride based compound semiconductor containing p-type impurities
In a conventional method of forming a pattern, an electron beam is accelerated and made to collide with a surface of a gallium nitride-based compound semiconductor layer containing a p-type impurity. The semiconductor layer which is made p-type by the electron beam is made p-type by the electron beam focused on the spot. The semiconductor layer to be converted into a p-type spot needs to be scanned with an electron beam in order to make the entire gallium nitride-based compound semiconductor layer having a large area p-type. Therefore, it takes time to make the gallium nitride-based compound semiconductor layer into a p-type in a wide area, and it is not possible to efficiently make a large number of gallium nitride-based compound semiconductor layers into a p-type. Further, in the method of converting a gallium nitride-based compound semiconductor layer into a p-type with an electron beam, it is necessary to dispose a gallium nitride-based compound semiconductor containing a p-type impurity in a vacuum and irradiate the electron beam. Therefore, the conventional method of converting a gallium nitride-based compound semiconductor into a p-type semiconductor requires
It is necessary to put in a container that can be tightly closed and create a vacuum,
Further, since an electron beam locally converts a very limited narrow region into p-type, the gallium nitride-based compound semiconductor layer containing p-type impurities can be efficiently formed, and further, a gallium nitride-based compound semiconductor containing p-type impurities can be formed. Multiple wafers with grown layers cannot be stacked and p-typed together. However, in the method for converting a gallium nitride-based compound semiconductor into a p-type according to the present invention, the gallium nitride-based compound semiconductor layer containing a p-type impurity is annealed to be p-type.
A plurality of wafers on which gallium nitride-based compound semiconductors containing p-type impurities have been grown can be converted into p-types easily, easily, extremely inexpensively and efficiently to form a bottom-resistant gallium nitride-based compound semiconductor layer. Realize ideal features.

Furthermore, the method for converting a gallium nitride-based compound semiconductor into a p-type semiconductor according to the present invention is characterized in that the gallium nitride-based compound semiconductor can be converted into a p-type in an ideal state to have an extremely low resistance state. This is because the method of the present invention grows and anneals a gallium nitride-based compound semiconductor layer containing a p-type impurity on a substrate via a buffer layer. The gallium nitride-based compound semiconductor layer grown on the substrate via the buffer layer becomes an excellent crystalline semiconductor layer due to the buffer layer. The p-type impurity contained in the gallium nitride-based compound semiconductor layer having an excellent crystal structure is bonded to hydrogen and hinders the formation of the p-type. However, when the hydrogen bonded to the p-type impurity is dissociated and removed by annealing, the p-type impurity normally functions as an acceptor, and the gallium nitride-based compound semiconductor layer having good crystallinity has a low resistance. This is a p-type layer. That is, by annealing the gallium nitride-based compound semiconductor layer having improved crystallinity in the buffer layer, the gallium nitride-based compound semiconductor layer becomes a lower resistance p-type gallium nitride-based compound semiconductor layer.

Further, the method of converting a gallium nitride-based compound semiconductor to a p-type according to the present invention has a feature that the entire surface of a gallium nitride-based compound semiconductor layer containing a p-type impurity can be uniformly converted to a p-type. This is because the gallium nitride-based compound semiconductor layer containing the p-type impurity is annealed to be p-type, so that the entire gallium nitride-based compound semiconductor layer is uniformly heated to be p-type during annealing. is there. A conventional gallium nitride-based compound semiconductor light-emitting device in which a gallium nitride-based compound semiconductor containing a p-type impurity is converted into a p-type by irradiating an electron beam is scanned with an electron beam that can only be locally converted into a p-type. Since it is p-type, it is extremely difficult to uniformly make the entire surface p-type. In particular, if the interval between electron beams scanned linearly is increased in order to increase the efficiency of p-type conversion, a problem arises in that the p-type cannot be reliably formed at the boundary of the scanning line. Conversely, if the interval between the electron beams scanned linearly is narrowed, the gallium nitride-based compound semiconductor layer having a large area cannot be efficiently made into a p-type. In the method for converting a gallium nitride-based compound semiconductor into a p-type according to the present invention, the gallium nitride-based compound semiconductor layer containing a p-type impurity is
It is not typed. The entire surface of the gallium nitride-based compound semiconductor layer that has been annealed to be p-type is uniformly heated to be p-type. This is extremely important when manufacturing a semiconductor wafer. The gallium nitride compound semiconductor light emitting device is large,
Since a wafer is manufactured and cut into small pieces to manufacture a gallium nitride-based compound semiconductor light emitting device chip, if the gallium nitride-based compound semiconductor layer is not uniformly p-type, the yield of the manufactured chip is reduced. This is because it is significantly reduced.

The gallium nitride-based compound semiconductor layer containing a p-type impurity is deeply p-type and more uniformly p-type as a whole, thereby realizing excellent light emitting characteristics. On the other hand, in a conventional gallium nitride-based compound semiconductor light emitting device in which a semiconductor layer containing a p-type impurity is converted to a p-type with an electron beam, the semiconductor layer containing a p-type impurity is the uppermost layer, and
Only the very surface is p-type and the resistance is reduced. This is because the accelerated electron beam cannot be deeply injected. In the method for converting a gallium nitride-based compound semiconductor to a p-type according to the present invention, the entire gallium nitride-based compound semiconductor containing a p-type impurity is heated to be p-type by annealing, so that the nitride containing the p-type impurity is nitrided. The entire gallium-based compound semiconductor layer is heated to be more uniformly p-type,
An extremely high-luminance light emitting element can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an annealing temperature and a resistivity according to an embodiment of the present invention.

FIG. 2 is a diagram showing the crystallinity of a p-type GaN layer according to one embodiment of the present invention in comparison with photoluminescence intensity.

FIG. 3 is a diagram showing the crystallinity of a p-type GaN layer according to one embodiment of the present invention in comparison with photoluminescence intensity.

Claims (3)

[Claims] 1. A step of growing a buffer layer on a surface of a substrate by a vapor phase growth method, and a step of growing a gallium nitride-based compound semiconductor layer containing a p-type impurity on a wafer on which the buffer layer has been grown. Annealing the wafer on which the buffer layer and the gallium nitride-based compound semiconductor layer have been grown to make the gallium nitride-based compound semiconductor layer containing p-type impurities into a p-type. A method of converting a semiconductor into a p-type. 2. The method according to claim 1, wherein the buffer layer is a GaN layer.
The method for converting a gallium nitride-based compound semiconductor into a p-type semiconductor according to the above. 3. A wafer, on which a buffer layer, an n-type gallium nitride-based compound semiconductor layer, and a gallium nitride-based compound semiconductor layer containing a p-type impurity are grown on a substrate. 2. The method for converting a gallium nitride-based compound semiconductor into a p-type semiconductor according to item 1.