JP2000269142A - Formation of gallium nitride epitaxial layer and light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize formation method of a GaN epitaxial layer, wherein the increase of manufacturing cost is restrained without generating large thermal strain between an obtained GaN epitaxial layer and a base layer. SOLUTION: In this forming method of a gallium nitride epitaxial layer, a gallium nitride epitaxial layer 2 is obtained by performing crystal growth for gallium nitride by a catalytic CVD method on a surface of a base layer 1. The gallium nitride epitaxial layer 2 can be obtained by forming a mask with an opening part for exposing the surface of the base layer 1, prior to crystal growth of gallium nitride by a catalyst CVD method and thereafter performing crystal growth for gallium nitride selectively by a catalyst CVD method on the surface of the base layer 1 which is exposed inside the opening part of the mask.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a gallium nitride epitaxial layer and a light emitting device in which a PN junction layer is formed from a gallium nitride epitaxial layer obtained by using this method.

[0002]

2. Description of the Related Art In recent years, gallium nitride (hereinafter referred to as GaN) has attracted attention as a crystal material of a light emitting layer (active layer) used in a high-brightness blue LED (light emitting diode), that is, a PN junction layer. The epitaxial layer as a GaN single crystal (however, the GaN epitaxial layer generally has many crystal defects.
The “aN epitaxial layer” is used in the sense that it includes a material having many crystal defects. In order to form (), a (0001) plane of a sapphire (Al ₂ O ₃ ) substrate or a (111) plane of a spinel (MgAl ₂ O ₄ ) substrate is usually used as a crystal substrate, and the MOCVD method (Metal Organic Chemical V
apor Deposition).

As a method of forming such an epitaxial layer of GaN, a case will be described in which a GaN epitaxial layer and a GaN: Mg epitaxial layer are formed on a sapphire substrate and a PN junction is formed from these layers to manufacture a light emitting diode. I do. In order to form an epitaxial layer of GaN on a sapphire substrate, first, the crystal orientation (0
A sapphire substrate having a surface of (001) and a thickness of about 0.5 mm is prepared. Next, the (0) of this sapphire substrate
001) surface is washed with a heated mixed acid (sulfuric acid + phosphoric acid),
Subsequently, the substrate is washed with pure water and dried.

Then, the sapphire substrate is subjected to MOCVD.
It is placed in the reaction chamber of the apparatus and fixed and held on a substrate holder (usually made of graphite). Subsequently, hydrogen is introduced into the reaction chamber to sufficiently discharge oxygen, nitrogen, and moisture. Further, while continuously introducing hydrogen, the temperature of the sapphire substrate is raised to about 1150 ° C. via the substrate holder by a heater provided in the substrate holder, and the state is maintained for about 10 minutes. By such high-temperature hydrogen treatment, residual organic contamination on the surface of the sapphire substrate and a strained layer of the sapphire substrate caused by mechanical processing can be removed.

Then, the temperature of the sapphire substrate is lowered to about 600 ° C. by adjusting the heating by the heater, and a source gas is flowed at the flow rate shown below to perform vapor phase growth for about 6 minutes, thereby forming a buffer layer on the sapphire substrate. A with a thickness of about 50 nm
A 1N layer is grown.・ Gas flow rate TMA (trimethylaluminum); 7 [μmol / min] NH ₃ ; 2.0 [SLM] H ₂ carrier; 2.5 [SLM]

Then, the temperature of the sapphire substrate is raised to about 1000 ° C. by adjusting the heating by the heater, and a source gas is flowed at a flow rate shown below to perform vapor phase growth for about 60 minutes. Ga of about 3 to 121 μm
A N epitaxial layer is grown.・ Gas flow rate TMG (trimethylgallium); 17 [μmol / min] NH ₃ ; 2.0 [SLM] H ₂ carrier; 2.5 [SLM]

Next, the respective flow rates of TMG, NH ₃ and H ₂ carriers are supplied as they are, and in addition, Cp
₂ Mg (Bis-cyclopentadienyl magnesium) is supplied into the reaction chamber such that the Mg concentration in the obtained GaN: Mg epitaxial layer becomes 2 × 10 ²⁰ / cm ³ .

When the source gas is supplied into the reaction chamber 51 in this manner, GaN:
Mg grows epitaxially, and a GaN: Mg epitaxial layer is obtained. The GaN: Mg epitaxial layer and the GaN epitaxial layer form a PN junction layer of a light emitting diode.

[0009]

However, such a method of forming a GaN epitaxial layer has the following disadvantages. The sapphire substrate and the obtained epitaxial layer have a thermal expansion coefficient of 7.5 × 10 ⁻⁶ / ° K for sapphire substrate and 5.59 × 1 for GaN (a-axis).
0 ^-6 / ° K. Since the formation of the GaN epitaxial layer is as high as about 1000 ° C. and at least 900 ° C. as described above, when the GaN epitaxial layer on the sapphire substrate thus obtained is returned to room temperature, the thermal expansion Due to the difference between the coefficients, a large thermal strain occurs between the substrate and the epitaxial layer.

The MOC used in the above-mentioned forming method is
In the VD method, since the reaction efficiency of source gases such as TMG and NH ₃ is as low as several percent or less, a large proportion of these source gases are discharged without being reacted, and the cost for recovering these gases is high. In addition, an increase in the use amount of the raw material gas itself causes an increase in manufacturing cost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a large thermal strain from occurring between an obtained GaN epitaxial layer and a base layer and to suppress an increase in manufacturing cost. Method for forming a GaN epitaxial layer and GaN obtained by the method
An object of the present invention is to provide a light emitting device using an epitaxial layer.

[0012]

In the method of forming a gallium nitride (GaN) epitaxial layer according to the present invention, it is an object of the present invention to obtain a gallium nitride epitaxial layer by growing gallium nitride on a surface of a base layer by catalytic CVD. Was the solution.

In the catalytic CVD method, energy for chemically reacting a raw material gas is basically supplied by a catalyst, and energy required in the base layer is an amount required for epitaxially growing (single crystal growth) the generated GaN on the surface of the base layer. Since only GaN is necessary to align along the crystal orientation of the base layer, the heating temperature of the base layer itself can be reduced to, for example, about 100 to 800 ° C. Therefore, according to this method of forming a GaN epitaxial layer, since epitaxial growth can be performed at a relatively low temperature, generation of large thermal strain between the obtained GaN epitaxial layer and the base layer is prevented.

Further, as described above, in the catalytic CVD method, the raw material gas is heated and activated by the catalyst, and the heating in the catalyst is performed at a high temperature at which the raw material gas is sufficiently activated, so that the reaction efficiency is increased. Can be increased, and an increase in the manufacturing cost can be suppressed.

In the light emitting device according to the present invention, the PN junction layer is formed by a gallium nitride epitaxial layer obtained by growing gallium nitride on the surface of the base layer by catalytic CVD. And

According to this light emitting device, a PN junction layer is formed on the GaN epitaxial layer obtained by the above-described method for forming an epitaxial layer. The manufacturing cost for forming the PN junction layer is also reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 is a view for explaining a first embodiment of a method for forming a GaN epitaxial layer according to the present invention. In FIG. 1, reference numeral 1 denotes a sapphire substrate, which serves as a base layer in the present invention.

For epitaxial growth (crystal growth) of GaN on the sapphire substrate 1, a thickness of about 0.5 mm having a crystal orientation (0001) plane as shown in FIG. A sapphire substrate 1 is prepared. Next, the crystal orientation of this sapphire substrate 1 (000
1) The surface is washed with a heated mixed acid (sulfuric acid + phosphoric acid), then washed with pure water and dried.

Next, Ga is applied to the (0001) plane by a catalytic CVD method using a catalytic CVD apparatus 50 shown in FIG.
N is crystal-grown, and a GaN epitaxial layer 2 is formed on the surface of the sapphire substrate 1 as shown in FIG.

Here, the catalytic CVD apparatus 50 shown in FIG.
The catalytic CVD apparatus 50 includes a reaction chamber 51 for processing an object to be processed and a front chamber 52 communicating therewith. Molecular pump 53, rotary pump 5
4 are connected in this order, and similarly, a turbo molecular pump 55 and a rotary pump 56 are connected to the front chamber 52 in this order.

The reaction chamber 51 is provided with a source gas pipe 57 connected to a deposition source gas supply source (not shown) via a reaction gas control system (not shown). The source gas for deposition is supplied into the chamber 51. In the reaction chamber 51, a substrate holder (susceptor) 58 for setting the sapphire substrate 1 to be processed is provided above the reaction chamber 51.
The substrate holder 58 is provided with a heater 59 and a thermocouple 60.

Under such a configuration, in the substrate holder 58, the sample can be heated by the heater 59 via the substrate holder 58, and the temperature of the substrate holder 58 can be detected by the thermocouple 60 to detect the temperature of the substrate. 59 can control the degree of heating. As the substrate holder 58, for example, a graphite susceptor is used.

A shutter 61 is provided below the substrate holder 58, and a catalyst 62 is further provided below the shutter 61.
Are arranged. The catalyst body 62 is made of, for example, a filament obtained by winding a thin tungsten wire in a coil shape, and is connected to a power supply 63 arranged outside the reaction chamber 51.
From now on, electric power is supplied, and
It is designed to be heated and held to about 00 ° C. The catalyst body 62 is disposed above a source gas supply port (not shown) in the reaction chamber 51 of the source gas pipe 58, and heats the deposition source gas supplied from the source gas pipe 58. Then, it is decomposed and activated.

In the reaction gas control system to which the source gas pipe 57 is connected, each gas supply source of TMG, TMA, NH ₃ , and H ₂ is connected to the reaction chamber 51 and an exhaust pump (not shown) through respective pipes. A mass flow controller (MFC) (not shown) and a regulating valve (not shown) are provided in the piping of each reaction gas.
The supply and stop of the gas into the inside and the flow rate thereof are controlled.

FIG. 3 is a view for explaining a second embodiment of the method for forming a GaN epitaxial layer according to the present invention. This embodiment differs from the first embodiment in that GaN is selectively epitaxially grown (crystal grown) on the sapphire substrate 1 to form a GaN epitaxial layer 2.

That is, in this example, first, FIG.
As shown in FIG. 1, a mask 4 having an opening 3 exposing the (0001) plane of the sapphire substrate 1 to be epitaxially grown is formed. As for the mask 4, a film (not shown) made of at least one of silicon oxide, silicon nitride, and silicon oxynitride is formed on the sapphire substrate 1 by a CVD method or the like, and then patterned by a known lithography technique or etching technique. It forms by doing.

Next, the sapphire substrate 1 on which the mask 4 has been formed in this manner is washed with a mixed acid (sulfuric acid + phosphoric acid) heated in the same manner as in the previous example, subsequently washed with pure water and dried. Next, GaN is selectively crystal-grown by the catalytic CVD method in the same manner as in the previous example by the catalytic CVD apparatus 50 shown in FIG. 2, and the GaN is grown in the opening 3 of the mask 4 as shown in FIG. Ga on the exposed surface of the sapphire substrate 1
An N epitaxial layer 2 is formed.

Here, the catalytic CVD apparatus 50 shown in FIG.
The method for selectively forming the GaN epitaxial layer 2 on the surface of the sapphire substrate 1 will now be described in detail. First, the sapphire substrate 1 on which the mask 4 is formed in the state shown in FIG.
2 and set on the substrate holder 58. Next, the turbo molecular pump 55 and the rotary pump 56 are operated to reduce the pressure inside the reaction chamber 51 to about 1 to 2 × 10 ⁻⁶ Pa,
This state is maintained for about 5 minutes, and in particular, moisture and oxygen brought into the reaction chamber 51 are exhausted.

Next, the substrate holder 58 is heated by the heater 59.
The sapphire substrate 1 through about 100 ° C. to 800 ° C.,
In this example, the temperature is maintained at 400 ° C. In addition, hydrogen flows from the reaction gas control system into the reaction chamber 51, and the flow rate and the pressure in the reaction chamber 51 are controlled to predetermined values. The pressure in the reaction chamber 51 is set to about 0.1 to 15 Pa, and is set to 1.0 Pa in this example. The flow rate is 400
[Sccm].

Next, the power is supplied to the catalyst 62 by turning on the power supply 63, and the temperature is raised to 1600 to 1800.
Increase to about ° C. In this example, the temperature is set to 1800 ° C. Then, this state is maintained for 10 minutes.

Next, TMG,
NH ₃ is also introduced into the reaction chamber 51. That is, in this example, the hydrogen flow rate is set to 250 [sccm],
The source gas is supplied into the reaction chamber 51 by setting the TMG flow rate to 1.7 [μmol / min] and the NH ₃ flow rate to 150 [sccm].

When the raw material gas is supplied into the reaction chamber 51 in this manner, the hydrogen atoms heated and activated by the catalyst body 62 etch the oxide film, so that the mask 4
On the surface of the sapphire substrate 1 facing the opening 3, the thin native oxide film formed here is removed by etching. Then, GaN is epitaxially grown on the surface of the sapphire substrate 1 exposed by removing the natural oxide film at a film formation rate of about 100 nm / min. In this example, the source gas is 40
The GaN epitaxial layer 2 having a thickness of 4.0 μm was formed by introducing the GaN epitaxial layer into the reaction chamber 51 for minutes.

On the mask 4, the catalyst 62
The hydrogen atoms activated by the etching of the surface of the mask 4 cause the surface of the mask 4 to be Ga within a certain time.
Since N is not deposited, the GaN epitaxial layer 2 is selectively formed on the surface of the sapphire substrate 1.

Here, the above-mentioned meaning that "GaN is not deposited on the surface of the mask 4 within a certain period of time" means that the foreign matter in the reaction chamber 51, the foreign matter in the source gas, Further, when GaN or the like, which is a reaction product, adheres to the surface of the mask 4, G
This is because aN may grow, meaning that GaN does not deposit on the surface of the mask 4 during the time in which such foreign substances serving as nuclei adhere to the surface of the mask 4. It is.

It should be noted that the mask 4 for a foreign substance or the like serving as a nucleus is specifically described.
The time required for the adhesion to the surface varies depending on the processing conditions and the like. However, under the conditions of this example, no GaN is deposited on the surface of the mask 4 even after the processing for 40 minutes, and therefore it is 40 minutes or more. It is presumed.

After the GaN is selectively epitaxially grown as described above, the TM is controlled by the reaction gas control system.
G, the flow rate of NH ₃ gas is set to zero, and only the hydrogen gas is kept flowing. Then, if this state is continued for 5 minutes, the catalyst body 6
Power supply to 2 is stopped to lower its temperature. Then
The flow rate of hydrogen gas was also reduced to zero, and
The pressure was reduced to about 2 × 10 × 10 ⁻⁶ Pa, this state was maintained for about 5 minutes, and especially TMG and NH introduced into the chamber.
Exhaust ₃ Thereafter, the sapphire substrate 1 is taken out of the atmosphere through the front chamber 52.

According to the method of forming the GaN epitaxial layer 2, it is necessary to utilize the fact that hydrogen atoms having a high energy or a group of hydrogen atoms activated by being thermally decomposed by the catalyst body 62 have a selective etching action. Sapphire substrate 1 without depositing GaN on mask 4
GaN can be selectively crystal-grown (epitaxially grown) only on the surface.

Further, since the source gas for deposition is activated by the catalyst body 62, the energy supplied from the sapphire substrate 1 can be reduced.
Temperature is, for example, 100 to 800 ° C.,
The temperature can be lower than 000 ° C.

In the above embodiment, a sapphire substrate is used as a base layer. However, the present invention is not limited to this. For example, spinel, GaN crystal, S
iC single crystal, SiC epitaxial layer, AlN epitaxial layer and the like can be used.
The GaN epitaxial layer can be selectively formed at a low substrate temperature of about 100 to 800 ° C. In the above example, hydrogen was used as the raw material gas in addition to TAG and NH ₃ , but instead of hydrogen, hydrogen chloride (HCl), chlorine (Cl ₂ ), hydrogen bromide (HBr), and bromine (Br ₂ ) were used. It can also be used.

Next, the light emitting device of the present invention will be described. FIG. 4 shows a light emitting device of the present invention as a light emitting diode (LE).
FIG. 5 is a diagram illustrating an example of an embodiment when applied to D), and reference numeral 10 in FIG. 4 denotes a light emitting diode. The light-emitting diode 10 has a sapphire substrate 11 having a thickness of about 300 μm.
A buffer layer 1 made of AlN and having a thickness of 50 nm or less
GaN epitaxial layer 1 having a thickness of about 3 μm
3 and a GaN: Mg epitaxial layer 14 having a thickness of about 500 nm or less is further formed thereon.

GaN epitaxial layer 13, GaN: M
The g-epitaxial layer 14 is formed by the above-described catalytic CVD.
The GaN epitaxial layer 13 is an N-type semiconductor crystal because it is not doped with impurities. On the other hand, the GaN: Mg epitaxial layer 14 has Mg in the GaN epitaxial layer. By being doped, a P-type semiconductor crystal is obtained. Therefore, the GaN epitaxial layer 13 and G
The aN: Mg epitaxial layer 14 has a PN junction layer formed thereon.

The GaN epitaxial layer 13 and the GaN: Mg epitaxial layer 14 have Al
The wiring 16 is provided via the electrode 15. A power supply (not shown) is connected to the wirings 16 and 16 such that the GaN epitaxial layer 13 side is a negative electrode and the GaN: Mg epitaxial layer 14 side is a positive electrode. With such a configuration, when a forward voltage is applied from the power supply, electrons from the N-type GaN epitaxial layer 13 and holes from the P-type GaN: Mg epitaxial layer 14 move to the PN junction in the light emitting diode 10. The electrons and holes recombine and emit light at that time. In other words, the free electrons are bound, and the free energy is emitted as light.

The GaN: Mg epitaxial layer 14
In this case, the portion where the Al electrode 15 is attached is subjected to an annealing process (L
An EEBI (Low-Energy Electron Beam Irradiation) process is performed to form an annealing portion 14a.

In order to manufacture the light emitting diode 10 having such a configuration, first, the prepared thickness 3
The 00 μm sapphire substrate 1 is washed with a heated mixed acid (sulfuric acid + phosphoric acid), subsequently washed with pure water and dried. Next, the sapphire substrate 1 is set on the substrate holder 58 via the front chamber 52 of the catalytic CVD device 50. Next, the inside of the reaction chamber 51 is depressurized to about 1 to 2 × 10 ⁻⁶ Pa by operating the turbo molecular pump 55 and the rotary pump 56, and this state is maintained for about 5 minutes, and particularly, the reaction chamber 51 is brought into the reaction chamber 51. Exhaust moisture and oxygen.

Next, the substrate holder 58 is heated by the heater 59.
The sapphire substrate 1 through about 100 ° C. to 800 ° C.,
In this example, the temperature is maintained at 400 ° C. In addition, hydrogen flows from the reaction gas control system into the reaction chamber 51, and the flow rate and the pressure in the reaction chamber 51 are controlled to predetermined values. The pressure in the reaction chamber 51 is set to about 0.1 to 15 Pa, and is set to 1.0 Pa in this example. The flow rate is 400
[Sccm].

Next, the power is supplied to the catalyst 62 by turning on the power supply 63, and the temperature is raised to 1600 to 1800.
Increase to about ° C. In this example, the temperature is set to 1800 ° C. Then, this state is maintained for 10 minutes.

Next, TMA,
While introducing NH ₃ into the reaction chamber 51, the flow rate of hydrogen is changed. That is, in this example, the hydrogen flow rate is set to 250 [s
ccm] and the TMA flow rate is 0.7 [μmol / mi.
n], the source gas is supplied into the reaction chamber 51 by setting the NH ₃ flow rate to 200 [sccm].

When the raw material gas is supplied into the reaction chamber 51 in this manner, the hydrogen atoms heated and activated by the catalyst body 62 etch the oxide film, so that the thin natural oxide formed on the surface of the sapphire substrate 1 is formed. The film is etched away. Then, AlN is epitaxially grown on the surface of the sapphire substrate 1 exposed by removing the natural oxide film at a deposition rate of about 50 nm / min. In this example, the buffer layer 12 made of an AlN epitaxial film having a thickness of 50 nm or less was formed by introducing a source gas into the reaction chamber 51 for one minute and performing epitaxial growth.

Next, TMA and NH ₃ were introduced into the reaction chamber 51.
Is stopped, the flow rate of hydrogen is set to 400 [sccm], and the pressure in the reaction chamber 51 is set to 1.0 Pa.
In particular, the TMA in the reaction chamber 51 is exhausted. When the TMA in the reaction chamber 51 is sufficiently exhausted in this way, TMG and NH ₃ are introduced into the reaction chamber 51 from the reaction gas control system, and the flow rate of hydrogen is changed. That is, the hydrogen flow rate was set to 250 [sccm], and the TMG flow rate was set to 1.7 [μmo.
1 / min] and a NH ₃ flow rate of 150 [sccm] to supply the source gas into the reaction chamber 51.

When the source gas is supplied into the reaction chamber 51 in this manner, GaN epitaxially grows on the surface of the buffer layer 12 formed on the sapphire substrate 1 at a film formation rate of about 100 nm / min. In this example, the source gas is 4
The GaN epitaxial layer 13 having a thickness of 4.0 μm was formed by introducing it into the reaction chamber 51 for 0 minutes and performing epitaxial growth.

Next, the NH ₃ flow rate was set to 200 [sccm].
To Cp ₂ Mg (Bis-cyclopentadien
yl magnesium) is supplied into the reaction chamber 51 such that the Mg concentration in the obtained GaN: Mg epitaxial layer 14 becomes 2 × 10 ²⁰ / cm ³ .

When the raw material gas is supplied into the reaction chamber 51 in this manner, G
aN: Mg is epitaxially grown at a film formation rate of about 50 nm / min. In this example, a GaN: Mg epitaxial layer 14 having a thickness of 500 nm or less was formed by introducing a source gas into the reaction chamber 51 for about 10 minutes and performing epitaxial growth.

After the GaN is selectively epitaxially grown as described above, the TM is controlled by the reaction gas control system.
The flow rates of the respective gases of G, NH ₃ and Cp ₂ Mg are set to zero, and only the hydrogen gas is kept flowing. Then, when this state is continued for 5 minutes, the power supply to the catalyst body 62 is stopped to lower the temperature. Next, the flow rate of the hydrogen gas was also reduced to zero, and the pressure inside the reaction chamber 51 was further reduced to about 1 to 2 × 10 × 10 ⁻⁶ Pa. This state was maintained for about 5 minutes, and particularly TMG and NH introduced into the chamber. _3. Exhaust Cp ₂ Mg. continue,
The sapphire substrate 1 is taken out of the atmosphere through the front chamber 52.

Next, the GaN: Mg epitaxial layer 1
No. 4 electrode-attached portions were annealed with an electron beam (LEEBI [Low-Energy Electron Beam Irradiatio
n] processing) is performed under the following conditions, and the annealing section 14a
To form -Annealing treatment conditions Beam spot size; 60 µm Current; 60 µA Acceleration voltage; 10 kV

Thereafter, the GaN: Mg epitaxial layer 1
4, an Al electrode 15 is formed at a predetermined portion of the annealing section 14a and the GaN epitaxial layer 13, and a wiring 16 is attached to the Al electrode 15 to obtain the light emitting diode 10 shown in FIG. The Al electrode 15 is formed by evaporating aluminum and then patterning the aluminum film by lithography and etching.

The light emitting diode 1 thus obtained
0, a GaN epitaxial layer 13 forming a PN junction layer and a GaN: Mg epitaxial layer 14
Is formed by the catalytic CVD method.
The aN epitaxial layer 13 and the GaN: Mg epitaxial layer 14 can be made good with little thermal strain. In the catalytic CVD method, the raw material gas is
Therefore, by heating the catalyst 62 at a high temperature such as 1800 ° C., the source gas can be sufficiently activated, and the reaction efficiency can be increased. Therefore, the manufacturing cost for forming the PN junction layer can be reduced as compared with the related art.

In the example shown in FIG. 4, the case where the light emitting device of the present invention is applied to a light emitting diode has been described. However, the present invention is not limited to this, and may be applied to, for example, a semiconductor laser. Can be.

[0058]

As described above, the method for forming a gallium nitride epitaxial layer according to the present invention is a method in which gallium nitride is crystal-grown by a catalytic CVD method to obtain a gallium nitride epitaxial layer. Can be epitaxially grown, thereby preventing a large thermal strain from being generated between the obtained GaN epitaxial layer and the base layer, and obtaining a good GaN epitaxial layer.

Further, in the catalytic CVD method, the raw material gas is heated and activated by the catalyst, and the reaction efficiency can be increased by heating the catalyst at a high temperature at which the raw material gas is sufficiently activated. Therefore, it is possible to suppress an increase in production cost due to a low reaction efficiency.

Prior to crystal growth of gallium nitride by the catalytic CVD method, a mask having an opening for exposing the surface of the base layer is formed, and thereafter, a mask is formed on the surface of the base layer exposed in the opening of the mask. If gallium nitride is selectively grown by catalytic CVD, a gallium nitride epitaxial layer can be selectively formed.

According to the light emitting device of the present invention, the PN junction layer is formed on the gallium nitride epitaxial layer obtained by the above-described method for forming an epitaxial layer. The PN junction layer can be made good, and the manufacturing cost of the PN junction layer can be reduced.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are side sectional views for explaining a first embodiment of a method for forming a gallium nitride epitaxial layer according to the present invention in the order of steps.

FIG. 2 is a schematic configuration diagram of a catalytic CVD apparatus used in the present invention.

FIGS. 3 (a) and 3 (b) are cross-sectional views of a main part for describing a second embodiment of a method of forming a gallium nitride epitaxial layer according to the present invention in the order of steps.

FIG. 4 shows a light emitting device of the present invention as a light emitting diode (LED).
It is a principal part sectional view which shows one Embodiment of this invention when applied to.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sapphire substrate, 2 ... GaN epitaxial layer, 3
... opening, 4 ... mask, 10 ... light emitting diode, 11 ...
Sapphire substrate, 12: buffer layer, 13: GaN epitaxial layer, 14: GaN: Mg epitaxial layer

Continued on the front page (72) Inventor Yuichi Sato 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Hideo Yamanaka 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sonny shares In-house F-term (reference) 5F041 AA40 CA02 CA23 CA34 CA40 CA46 CA49 CA57 CA64 CA67 5F045 AB14 AB32 AB33 AB34 AC07 AC12 AD05 AD06 AD07 AD08 AD09 AD10 AD11 AD12 AE19 AE21 AE23 AF02 AF04 AF09 BB07 CA09 CA10 DB02 DP05 EK08 HA04

Claims (5)

[Claims] 1. A method for forming a gallium nitride epitaxial layer, wherein gallium nitride is grown on a surface of a base layer by catalytic CVD to obtain a gallium nitride epitaxial layer. 2. A mask having an opening for exposing the surface of the base layer is formed before crystal growth of gallium nitride by the catalytic CVD method, and thereafter, the mask is formed on the surface of the base layer exposed in the opening of the mask. 2. The method for forming a gallium nitride epitaxial layer according to claim 1, wherein gallium nitride is selectively grown by catalytic CVD to obtain a gallium nitride epitaxial layer. 3. The method for forming a gallium nitride epitaxial layer according to claim 2, wherein said mask is made of at least one of silicon oxide, silicon nitride, and silicon oxynitride. 4. The gallium nitride epitaxial layer according to claim 1, wherein said base layer is made of at least one of sapphire, spinel, gallium nitride crystal, SiC single crystal, SiC epitaxial layer and AlN epitaxial layer. Method. 5. A light-emitting element comprising a gallium nitride epitaxial layer obtained by growing gallium nitride on a surface of a base layer by catalytic CVD and forming a PN junction layer.