JP2003060318A - GaN COMPOUND SEMICONDUCTOR EPITAXIAL WAFER AND SEMICONDUCTOR DEVICE USING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high quality crystallinity in an epitaxial layer (device layer), in a GaN compound semiconductor epitaxial wafer having an off-angle. SOLUTION: A substrate 11 and a device layer 12 are provided, and the substrate 11 consists of a first nitride semiconductor belonging to a hexagonal system, and the device layer 12 consists of a second nitride semiconductor belonging to a hexagonal system for forming a semiconductor device, formed through growth on the main surface of the substrate 11. The plane orientation of the main surface of the substrate 11 has the off-angle in the direction <1-100> from the (0001) surface, and the device layer 12 has the surface form of stripes, extending nearly in parallel to the off-angle direction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a GaN-based semiconductor element such as a GaN-based blue-violet semiconductor laser device, a GaN-based light-emitting diode device capable of emitting light in the ultraviolet to red region, or a GaN-based high-frequency electronic device. The present invention relates to a GaN-based compound semiconductor epitaxial growth wafer used for forming a semiconductor device.

[0002]

2. Description of the Related Art A nitride semiconductor containing nitrogen (N) as a group V element has a relatively large band gap,
It is regarded as a promising material for short-wavelength light emitting devices. Among them, the general formula Al _x Ga _y In _z N (where, 0 ≦ x, y,
For gallium nitride (GaN) -based compound semiconductors represented by z ≦ 1, x + y + z = 1), blue light emitting diode (LED) elements and green light emitting diode elements have already been put to practical use. ing.

In addition, HD-DVD (High Definition)
Nation Digital Versatile
As a light source for next-generation high-density optical discs such as Disk)
There is a strong demand for a blue-violet semiconductor laser device having an oscillation wavelength of about 400 nm, and research and development of a semiconductor laser device using a gallium nitride-based semiconductor material have been actively conducted.

FIG. 5 is a partially enlarged perspective view of an epitaxial growth wafer (hereinafter referred to as an epi wafer) used for a conventional gallium nitride compound semiconductor device.

As shown in FIG. 5, gallium nitride (Ga
The plane orientation of the main surface of the substrate 101 made of N) is (000
It has an off angle of 0.2 ° in the <1-100> direction of the crystal zone axis from the 1) plane. An element layer 1 made of an epitaxially grown gallium nitride-based semiconductor is formed on the main surface of the substrate 101.
02 is formed.

The surface morphology (surface morphology) of the element layer 102 is influenced by a step (not shown) on the surface of the substrate 101, and has a plurality of steps appearing in the same direction (= <1-100> direction). is doing. That is, a plurality of steps are formed in a direction having an off angle with respect to the plane orientation of the main surface of the substrate 101. In the specification of the present application, a negative sign "-" added to the index of the plane orientation or the crystal zone axis conveniently represents the inversion of one index following the negative sign.

When a semiconductor laser device is manufactured by using such an epi-wafer, the laser resonance direction and the step direction (= <1-100> direction) in the resonator forming the waveguide are substantially perpendicular to each other. Is formed in. Here, if the resonance direction (stripe direction) of the resonator is aligned with the step direction (off-angle direction) of the substrate 101, the heights of the end faces of the resonator facing each other shift due to each step, and Loss (waveguide loss) increases. Therefore, the threshold current of the laser element increases, and as a result, the reliability also decreases.

By the way, in Japanese Unexamined Patent Publication No. 2000-156348, an element layer having a step having a width of a flat portion (terrace portion) sandwiched between adjacent step portions of several hundreds to several thousands μm is formed. A GaN-based compound semiconductor epiwafer is described.

In the above publication, GaN (1-10
0) The resonance direction is set in a direction parallel to the step direction so that the M plane can be cleaved. Therefore, the width of the terrace is
It is necessary to make it at least larger than the length dimension of one side of the chip that can be cut out as a chip.

[0010]

However, the GaN-based compound semiconductor epiwafer according to the above publication has an off-angle of 0.3 ° to 0.5 so that a terrace portion enough to obtain a laser chip is formed. It is necessary to make it extremely small, about 0 °.

Therefore, for example, since the off angle cannot be made larger than 1 °, the surface morphology of the epi-wafer is deteriorated and the half width of the X-ray rocking curve which is an index of crystal orientation is increased. Then, there is a problem that an element layer having high quality crystallinity cannot be obtained. Therefore, the characteristics of the semiconductor device manufactured using the conventional GaN-based compound semiconductor epiwafer are also insufficient.

An object of the present invention is to solve the above conventional problems and to obtain high quality crystallinity in an epitaxial layer (element layer) in a GaN-based compound semiconductor epitaxial wafer having an off angle.

[0013]

In order to achieve the above object, a GaN-based compound semiconductor epiwafer according to the present invention comprises:
A substrate made of a first nitride semiconductor belonging to a hexagonal system,
An element layer formed by growth on the main surface of the substrate and made of a second nitride semiconductor belonging to the hexagonal system for forming a semiconductor element, and the plane orientation of the main surface of the substrate is (0001).
The element layer has an off-angle in one direction from the plane, and the element layer has a striped surface morphology extending substantially parallel to the one direction.

According to the GaN-based compound semiconductor epitaxial wafer of the present invention, since the element layer has a striped surface morphology extending substantially parallel to one direction having an off angle, the off angle of the substrate is reduced. Even if it is increased to 1 ° or more, the width between the stripes (width of the terrace portion) never narrows. Therefore, the surface morphology (surface morphology) of the element layer becomes good, and the element layer having excellent crystallinity can be obtained. The striped surface morphology is a step formed by one or two atomic layers appearing on the surface of the element layer.

In the GaN compound semiconductor epiwafer of the present invention, it is preferable that one direction is the <1-100> direction of the zone axis.

In the GaN compound semiconductor epitaxial wafer of the present invention, it is preferable that the off angle is 1 ° or more and 10 ° or less.

A semiconductor device according to the present invention is a substrate made of a first nitride semiconductor belonging to a hexagonal system and a hexagonal system for forming a semiconductor device, which is formed by growth on the main surface of the substrate. Targeting a semiconductor device using a GaN-based compound semiconductor epiwafer having a device layer made of a second nitride semiconductor, the plane orientation of the main surface of the substrate has an off angle in one direction from the (0001) plane, The element layer has a striped surface morphology that extends substantially parallel to one direction.

According to the semiconductor element of the present invention, since the element layer has a striped surface morphology extending substantially parallel to one direction having an off angle, the off angle of the substrate is 1 ° or more. Even if it is increased, the width of the stripes does not become narrow, so that the surface morphology of the element layer becomes good, and the element layer excellent in crystallinity can be obtained.

In the semiconductor device of the present invention, one direction is preferably the <1-100> direction of the crystal zone axis.

In the semiconductor device of the present invention, the off angle is 1
It is preferable that the angle is not less than 0 and not more than 10 °.

The semiconductor device of the present invention is preferably a laser device.

In this case, it is preferable that the laser element has a resonator formed substantially parallel to one direction.

In this case, the off angle is 1 ° or more and 10 °
It is below, and it is preferable that the end face of the resonator is formed by cleavage.

The semiconductor device of the present invention is preferably a light emitting diode device.

[0025]

(First Embodiment) First Embodiment of the Present Invention
Embodiments will be described with reference to the drawings.

FIG. 1 shows Ga according to the first embodiment of the present invention.
As shown in FIG. 1, which is a partially enlarged perspective view of an N-based compound semiconductor epi-wafer, in the epi-wafer 10 according to the first embodiment, the crystal system belongs to the hexagonal system and its main surface is (0
A substrate 11 made of gallium nitride (GaN) having an off-angle tilted from the (001) plane in the <1-100> direction of the crystal zone axis by about 5 °, and a metal-organic pyrolysis gas is formed on the main surface of the substrate 11. Phase growth (MOVPE: Metalorganic V)
an element layer 1 made of a GaN-based compound semiconductor belonging to a hexagonal crystal system for forming a semiconductor element, which is epitaxially grown by an apor phase epitaxy method or the like.
2 and.

The surface morphology of the element layer 12 is a stripe shape extending substantially parallel to the <1-100> direction of the crystal zone axis, and the interval between the stripes is about 10 μm to 20 μm.

The substrate 11 is not limited to liquid phase, vapor phase or solid phase growth, but here, for example, high temperature high pressure method, MOVPE method, or hydride vapor phase growth (H) method is used.
VPE: Hydride Vapor Phase E
Pitaxy) method or the like.

When the X-ray rocking curve of the epi-wafer 10 having the device layer 12 was measured, its half-value width was about 1.
It has been confirmed that it is less than 00 seconds. As described above, in the conventional epi-wafer, the off-angle of the main surface is smaller than 1 °, and the half width of the X-ray rocking curve in this case is about 20.
It is 0 to 300 seconds. Therefore, it can be seen that the epi-wafer 10 according to the first embodiment has significantly improved crystallinity as compared with the conventional epi-wafer having an off angle smaller than 1 °.

Thus, the substrate 1 made of gallium nitride
The surface morphology of the element layer 12 formed by epitaxial growth on the substrate 11 is set to be in the range of <1-100 in the off-angle direction by setting the off-angle of 1 to several degrees, for example, in the range of 1 ° or more and 10 ° or less. It has been confirmed that the stripe shape extends substantially parallel to the> direction, and as a result, the crystallinity of the element layer 12 is significantly improved.

In the first embodiment, MOVPE is used as an epitaxial growth method for forming the element layer 12.
However, the present invention is not limited to this, and other epitaxial growth methods such as molecular beam epitaxy (MBE: Molecu) are used.
It goes without saying that the present invention can be realized by using the lar Beam Epitaxy method or the HVPE method.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows Ga according to the second embodiment of the present invention.
The partial cross-sectional structure of the N-type compound semiconductor epi-wafer is shown.

In FIG. 2, Ga according to the second embodiment
The element layer 12 made of an N-based compound semiconductor is an epitaxial layer having a semiconductor laser structure capable of emitting violet light.

As shown in FIG. 2, the GaN-based compound semiconductor epi-wafer 10 has gallium nitride whose main surface is off-angled by about 2 ° from the (0001) plane in the <1-100> direction of the crystal zone axis ( GaN) on the main surface of the substrate 11,
an n-type semiconductor layer 21 made of n-type GaN, an n-type cladding layer 22 made of n-type aluminum gallium nitride (AlGaN), an n-type light guide layer 23 made of n-type GaN,
Well layer made of indium nitride (InGaN) and Ga
A multiple quantum well (MQW) active layer 24 in which a plurality of barrier layers made of N are stacked, and a p layer made of p-type AlGaN
Type cap layer 25, p type optical guide layer 26 made of p type GaN, and p type cladding layer 27 made of p type AlGaN
And a p-type contact layer 28 made of p-type GaN are sequentially stacked by epitaxial growth.

N-type clad layer 22 and p-type clad layer 2
Reference numeral 7 confines carriers injected into the MQW active layer 24 and recombination light by the carriers, and the n-type optical guide layer 23
The p-type light guide layer 26 improves the efficiency of confining carriers and recombination light. In addition, the p-type cap layer 25
Serves as a barrier layer that prevents electrons injected from the n-type semiconductor layer 21 from leaking to the p-type light guide layer 26 without being injected into the MQW active layer 24.

The resonance direction (longitudinal direction) of the resonator is perpendicular to the M plane so that the cleaved end face of the resonator provided in the semiconductor laser structure is the M plane of the crystal plane of gallium nitride. The <1-100> direction of the band axis.

Here, the off-angle direction of the substrate 11 is also <1-1.
00> direction, the surface morphology of the element layer 12 epitaxially grown on the substrate 11 has a striped pattern extending in a direction substantially parallel to the off-angle direction (<1-100> direction) as described above. Therefore, the longitudinal direction of the resonator, the so-called stripe direction, and the direction in which the striped pattern extends coincide. Therefore, the width between the adjacent stripes (terrace part) is 10 μm to 20 μm, and
Since the resonator width is about 2 μm to 3 μm, the resonator can be reliably formed on the terrace portion.

In the second embodiment, the substrate 1
The off angle on the principal surface of No. 1 is about 2 °, but it may be 1 ° or more and 10 ° or less.

The MQW active layer 24 has a well layer of In.
Although GaN and the barrier layer are GaN, the well layer may be GaN and the barrier layer may be AlGaN instead.

The n-type clad layer 22 and the p-type clad layer 27 have a single layer structure of AlGaN instead of A
It may be a superlattice clad layer composed of a laminated body of an lGaN layer and a GaN layer. Here, when the superlattice cladding layer is used, the impurity doping such as silicon (Si) which is an n-type dopant or magnesium (Mg) which is a p-type dopant is applied to at least one of the AlGaN layer and the GaN layer. You can do it.

(Third Embodiment) A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows Ga according to the third embodiment of the present invention.
The partial cross-sectional structure of the N-type compound semiconductor epi-wafer is shown.

In FIG. 3, Ga according to the third embodiment
The element layer 12 made of an N-based compound semiconductor is an epitaxial layer having a light emitting diode structure capable of emitting blue light.

As shown in FIG. 3, the GaN-based compound semiconductor epi-wafer 10 has gallium nitride () whose main surface is off-angled by about 2 ° from the (0001) plane in the <1-100> direction of the crystal zone axis. GaN) on the main surface of the substrate 11,
n-type semiconductor layer 41 made of n-type GaN and n-type InGa
An n-type superlattice clad layer 42 made of a laminate of N layers and an n-type GaN layer, a multiple quantum well (MQW) active layer 43 made up of a plurality of well layers made of InGaN and barrier layers made of GaN, A p-type cap layer 44 made of p-type AlGaN, a p-type superlattice cladding layer 45 made of a laminate of a p-type AlGaN layer and a p-type GaN layer, and a p-type G
It has a structure in which a p-type contact layer 46 made of aN is sequentially laminated by epitaxial growth.

Also in the third embodiment, the surface morphology of the element layer 12 is in the off-angle direction (<1-100> direction).
And a striped pattern extending in a direction substantially parallel to
The full width at half maximum of the line rocking curve is reduced to about 80 seconds, and the crystallinity is remarkably improved as compared with the conventional case. as a result,
G produced using the epi-wafer according to the third embodiment
It has been confirmed that the luminous efficiency of the aN-based blue light emitting diode element is significantly increased.

The substrate 1 is also used in the third embodiment.
Although the off angle on the principal surface of No. 1 is about 2 °, it may be 1 ° or more and 10 ° or less.

The MQW active layer 43 has a well layer of In.
Instead of GaN and the barrier layer GaN, the well layer may be GaN and the barrier layer may be AlGaN.

The n-type cladding layer 42 is made of n-type InG.
The superlattice structure is formed of a laminated body of an aN layer and an n-type GaN layer, but instead of this, an n-type AlGaN layer and an n-type GaN are used.
Superlattice structure with layers, or n-type GaN or n-type AlG
A single layer structure made of aN may be used.

The p-type cladding layer 45 is made of p-type AlG.
Although a superlattice structure including a laminated body of an aN layer and a p-type GaN layer is used, p-type GaN or p-type AlGaN may be used instead.
It may be a single layer structure consisting of.

Here, as in the case of the second embodiment, when each clad layer has a superlattice structure, the n-type dopant or p-type dopant impurity doping is performed in the well layer and barrier in the superlattice structure. It may be done for at least one of the layers.

[0052]

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 shows a second embodiment of the present invention.
3 is a perspective view of a violet semiconductor laser device manufactured using the GaN-based compound semiconductor epiwafer according to the embodiment of FIG.

The first embodiment relates to a crystal growth method for device layers,
The growth pressure is reduced to 300 Torr (1 Torr
= 133.322 Pa) is used.

Trimethyl aluminum is a Group III source.
(TMAl: (CH₃)₃ Al), trimethylgallium
(TMGa: (CH₃)₃ Ga) or trimethylindiu
(TMIn: (CH₃)₃ In) is used as the source gas
There is. In addition, ammonia (NH₃ ) Use gas
There is. Examples of the n-type impurity raw material include monosilane (Si
H _Four ) Is used as the p-type impurity source, for example,
N-dienyl magnesium (Cp₂ Mg: (C_FiveH_Five)₂M
g) is used. The carrier gas for these source gases is
Hydrogen (H₂ ) Gas and nitrogen (N₂ ) Use gas.

The main surface of the element layer substrate is (000
1) A substrate 11 made of gallium nitride (GaN) having an off angle inclined by about 2 ° in the <1-100> direction from the plane is used.

First, an example of the growth process of the element layer 12 shown in FIG. 2 will be described.

After the substrate 11 was put into the reaction chamber of the MOVPE apparatus, the substrate 11 was grown at a temperature of about 1 which is the growth temperature of the element layer 12.
Heat to 050 ° C. Here, the supply of the NH ₃ gas is started at the time when the substrate temperature reaches about 400 ° C. so that the surface of the substrate 11 is not transformed by heat. After the substrate temperature reached about 1050 ° C. and several minutes later, the supply of TMGa and SiH ₄ gas was started, and the substrate 11 was covered with n-type GaN having a thickness of about 3 μm on the main surface. The n-type semiconductor layer 21 is grown. Then, the supply of TMAl is started and the thickness of the n-type semiconductor layer 21 is about 0.
An n-type clad layer 22 made of 7 μm n-type AlGaN is grown. Then, the supply of TMAl is stopped and the n-type optical guide layer 23 made of n-type GaN having a thickness of about 10 nm is grown.

After that, the growth temperature is lowered to about 800 ° C., and then the MQW active layer 24 is grown on the n-type optical guide layer 23. Specifically, TMGa, TMIn and NH ₃
Is supplied to grow a well layer made of InGaN having a thickness of about 3 nm, and TMGa and NH ₃ are supplied to grow a barrier layer made of GaN having a thickness of about 7.5 nm. The layers and the barrier layers are alternately stacked to obtain three pairs of MQW active layers 24.

Subsequently, the growth temperature is raised to 1000 ° C.
After that, TMAl, TMGa, NH ₃ And Cp₂ Mg
By supplying, the thickness on the MQW active layer 24 is increased.
A p-type cap layer 25 made of p-type AlGaN having a thickness of about 2 nm
To grow. After that, the supply of TMAl is stopped and the p-type
On the cap layer 25, p-type GaN having a thickness of about 10 nm
The p-type light guide layer 26 of is grown. Then TM
After the supply of Al is restarted, the Al on the p-type light guide layer 26
And a p-type made of p-type AlGaN having a thickness of about 0.5 μm
The clad layer 27 is grown. Then, supply TMAl
Stop, and the thickness is about 0.2 on the p-type cladding layer 27.
Grow a p-type contact layer 28 of μm p-type GaN
To do.

Subsequently, a p-type contact layer 28 was grown.
After that, the source gases TMGa and CP ₂ Mg and NH₃ of
Stop the supply, N₂ And H₂ Carrier gas consisting of
While supplying it as it is, cool it to room temperature, then
The wafer 10 is taken out of the reaction chamber.

As shown in FIG. 1, the surface morphology of the epi-wafer 10 according to the first embodiment thus formed has the off-angle direction of the main surface of the substrate 11, that is, <1 of the crystal zone axis. A striped pattern extending in a direction substantially parallel to the −100> direction is shown.

The full width at half maximum of the X-ray rocking curve obtained from the epi-wafer 10 is about 80 seconds.

Next, an example of a method for manufacturing the violet semiconductor laser device shown in FIG. 4 will be described with reference to the drawings.

First, p or p is formed by a sputtering method or a CVD method.
Silicon oxide (SiO 2) is formed on the entire surface of the mold contact layer 28.
₂ ) After depositing a mask forming film (not shown) consisting of
The mask forming film is patterned into a ridge stripe shape by a lithography method, and a mask film for dry etching is formed from the mask forming film. Then, the p-type contact layer 28 and the p-type clad layer 27 are etched by the reactive ion etching method using the formed mask film to the extent that the p-type optical guide layer 26 is exposed, and the p-type contact layer 28 and The ridge stripe shape of the mask film is transferred to the p-type clad layer 27.

Next, after removing the mask film, the upper and side surfaces of the p-type contact layer 28 and the p-type cladding layer 27 that have been etched, and the exposed p-type light guide layer 26,
A protective insulating film 29 made of silicon oxide is deposited, and then an opening for exposing the p-type contact layer 28 is selectively formed in the protective insulating film 29 by the lithography method and the dry etching method.

Next, a resist pattern having an opening in the exposed region of the p-type contact layer 28 is formed by the lithography method. Then, nickel (N
After i) and gold (Au) are sequentially deposited, a p-side electrode 30 made of a laminated body of Ni and Au and in ohmic contact with the p-type contact layer 28 is formed by a lift-off method.

Next, the surface (back surface) of the substrate 11 opposite to the element layer 12 is polished until the thickness thereof becomes about 100 μm. After that, titanium (Ti) and aluminum (Al) are sequentially vapor-deposited on the back surface by a vapor deposition method or the like to form an n-side electrode 31 made of a laminate of Ti and Al and in ohmic contact with the substrate 11.

Next, the epi-wafer 10 is cleaved along the M-plane to form a bar-shaped semiconductor laminated body including a plurality of resonators and exposing the end faces of each resonator. After that, the reflection end face (rear face) of the cleaved surface is coated with a high reflection film made of a dielectric film having a reflectance of about 80%, and the emission end face (front face), which is the opposing face, has a reflectance of about A low reflection film composed of a 20% dielectric film is coated. Then, the bar-shaped semiconductor laminated body is divided into chips so as to include at least one resonator.

The GaN-based violet semiconductor laser device thus manufactured had an oscillation wavelength of 405 nm. When the output characteristics and the current characteristics of the laser light were evaluated, the threshold current was about 45 mA, and the threshold current was about 45 mA. Good characteristics with a voltage of about 4.5 V are obtained. This gives a light output of 3
Since the operating current and the operating voltage at 0 mW can also be reduced, the injection power is reduced, so that the reliability is improved and the life can be extended.

The MQW active layer 24 is composed of a well layer made of InGaN and a barrier layer made of GaN, but instead of this, a well layer made of GaN or AlGaN and a barrier layer made of n-type AlGaN. When configured by and, laser light having an oscillation wavelength in the ultraviolet region can be obtained.

Further, in the first embodiment, neither the well layer nor the active layer of the MQW active layer 24 is doped with n-type impurities, but due to diffusion from the n-type optical guide layer 23 during growth. It may exhibit n-type conductivity. However, M
At the time of growing the QW active layer 24, at least one of the well layer and the active layer may be positively doped with impurities.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

The second example is Ga according to the second embodiment.
An example of a method for manufacturing a blue light emitting diode element manufactured using an N-based compound semiconductor epiwafer will be shown.

Also in this case, MOVPE is used as the crystal growth method for the device layer, in which the growth pressure is 300 Torr, which is a reduced pressure.
Use the method.

As the group III source, a source gas made of trimethylaluminum (TMAl), trimethylgallium (TMGa) or trimethylindium (TMIn) is used as in the first embodiment. Ammonia (NH ₃ ) gas is used as the group V source. Monosilane (SiH ₄ ) is used as the n-type impurity raw material, and cyclopentadienyl magnesium (Cp ₂ ) is used as the p-type impurity raw material.
Mg) is used. Further, hydrogen gas and nitrogen gas are used as carrier gases for these source gases.

The main surface of the substrate on which the element layer is grown is (00
Substrate 11 made of gallium nitride (GaN) having an off-angle tilted from the (01) plane in the <1-100> direction by about 5 °
To use.

First, the substrate 11 is placed in the reaction chamber of the MOVPE apparatus.
Substrate 11 at the growth temperature of the device layer 12
Heat to about 1050 ° C. Here, the table of the substrate 11
The substrate temperature should be 400 ° C so that the surface is not transformed by heat.
When it reaches about ℃, NH ₃ Start gas supply.
Substrate temperature reaches about 1050 ° C, and several minutes later
After passing, TMGa and SiH_Four Start supplying with gas
Then, on the main surface of the substrate 11, n-type GaN having a thickness of about 3 μm is formed.
The n-type semiconductor layer 41 made of is grown.

Then, on the n-type semiconductor layer 41, an n-type G
An n-type superlattice cladding layer 42 made of aN / undoped InGaN is grown. Specifically, by supplying TMGa, NH ₃ and SiH ₄ , the film thickness is about 2.5 nm.
A barrier layer made of n-type GaN of TMGa, TM
By supplying In and NH ₃ , the thickness is about 2.5.
A well layer made of undoped InGaN having a thickness of nm is grown, and these barrier layers and well layers are alternately laminated.

After that, the growth temperature is lowered to about 800 ° C., and then the MQW active layer 43 is grown on the n-type superlattice cladding layer 42. Specifically, TMGa, by supplying TMIn and NH _3, the film thickness of about 3 nm an In
By growing a well layer made of GaN and supplying TMGa, NH ₃ and SiH ₄ , a barrier layer made of n-type GaN having a thickness of about 7.5 nm is grown, and the well layers and the barrier layers are alternately formed. By stacking, 5 pairs of MQW active layers 43 are obtained.

Subsequently, the growth temperature is raised to 1000 ° C.
After that, TMAl, TMGa, NH ₃ And Cp₂ Mg
By supplying, the thickness on the MQW active layer 43 is increased.
A p-type cap layer 44 made of p-type AlGaN having a thickness of about 2 nm
To grow.

Then, a p-type superlattice cladding layer 45 made of p-type AlGaN / undoped GaN is grown on the p-type cap layer 44. Specifically, TMGa, TMA
l, NH ₃ and Cp ₂ Mg are supplied to grow a barrier layer of p-type AlGaN having a film thickness of about 2.5 nm, and TMGa and NH ₃ are supplied to provide a thickness of about 2.5 nm. , A well layer made of GaN is grown, and the barrier layers and the well layers are alternately laminated.

Next, by supplying TMGa, NH ₃ and Cp ₂ Mg, a p-type contact layer 46 of p-type GaN having a thickness of about 0.2 μm is formed on the p-type superlattice cladding layer 45. grow up.

Next, although not shown, a p-side electrode is formed on the p-type contact layer, an n-side electrode is formed on the surface of the substrate 11 opposite to the element layer 12, and then the substrate is formed. Divide 11 into chips of desired size.

As shown in FIG. 1, the surface morphology of the epi-wafer 10 according to the second embodiment thus formed has the off-angle direction of the main surface of the substrate 11, that is, <1.
A striped pattern extending in a direction substantially parallel to the −100> direction is shown.

Further, the full width at half maximum of the X-ray rocking curve obtained from the epi-wafer 10 is about 80 seconds, which shows that good crystallinity is exhibited.

The n-type superlattice cladding layer 42 was doped with impurities only in the GaN layer as a barrier layer, and the p-type superlattice cladding layer 45 was also doped with impurities only in the AlGaN layer as a barrier layer. At least one of the barrier layer and the well layer may be doped.

Although the MQW active layer 43 is doped with impurities only in the GaN layer which is the barrier layer, at least one of the barrier layer and the well layer may be doped, and both the barrier layer and the well layer may be doped. It may be undoped.

As described above, the superlattice layers 42, 4
5 and the MQW active layer 43 are not substantially doped with impurities during crystal growth. However, impurities may be included in the undoped layer due to diffusion of impurities from the semiconductor layer adjacent to these undoped layers and doped with impurities during or after crystal growth. Therefore, in the present specification, the undoped layer is not limited to a semiconductor layer that is not substantially doped with impurities during crystal growth, but a semiconductor layer that has impurities contained in an adjacent semiconductor layer as a result of diffusion. Also says.

[0090]

According to the GaN compound semiconductor epi-wafer of the present invention and the semiconductor device manufactured using the epi-wafer, the width of the stripes becomes narrow even if the off-angle of the substrate is increased to 1 ° or more. Since it is not present, the surface morphology of the element layer becomes good, and the element layer having excellent crystallinity can be obtained.

[Brief description of drawings]

FIG. 1 is a partial enlarged perspective view showing a GaN-based compound semiconductor epitaxial wafer according to a first embodiment of the present invention.

FIG. 2 is a partial structural cross-sectional view of a GaN-based compound semiconductor epitaxial wafer according to a second embodiment of the present invention.

FIG. 3 is a partial structural cross-sectional view of a GaN-based compound semiconductor epitaxial wafer according to a third embodiment of the present invention.

FIG. 4 is a perspective view showing a violet semiconductor laser device manufactured using the GaN-based compound semiconductor epiwafer according to the first embodiment of the present invention.

FIG. 5 is a partial enlarged perspective view showing a conventional GaN-based compound semiconductor epitaxial wafer.

[Explanation of symbols]

10 Epiwafer 11 board 12 element layers 21 n-type semiconductor layer 22 n-type clad layer 23 n-type optical guide layer 24 Multiple quantum well (MQW) active layer 25 p-type cap layer 26 p-type optical guide layer 27 p-type clad layer 28 p-type contact layer 29 Protective insulation film 30 p side electrode 31 n-side electrode 41 n-type semiconductor layer 42 n-type superlattice cladding layer 43 Multiple quantum well (MQW) active layer 44 p-type cap layer 45 p-type superlattice cladding layer 46 p-type contact layer

Claims (10)

[Claims] 1. A substrate made of a first nitride semiconductor belonging to the hexagonal system, and a second nitride belonging to the hexagonal system, which is formed on the main surface of the substrate by growth to form a semiconductor device. An element layer made of a semiconductor, and a plane orientation of a main surface of the substrate has an off angle in one direction from a (0001) plane, and the element layer extends substantially parallel to the one direction. A GaN-based compound semiconductor epiwafer having a striped surface morphology. 2. The one direction is <1-100 of a crystal zone axis.
> Direction. GaN according to claim 1, wherein
Compound semiconductor epiwafer. 3. The Ga according to claim 1, wherein the off angle is 1 ° or more and 10 ° or less.
N-based compound semiconductor epi-wafer. 4. A substrate made of a first nitride semiconductor belonging to the hexagonal system, and a second nitride belonging to the hexagonal system for forming a semiconductor device, which is formed on the main surface of the substrate by growth. A semiconductor device using a GaN-based compound semiconductor epiwafer having a device layer made of a semiconductor, wherein the plane orientation of the main surface of the substrate has an off-angle in one direction from the (0001) plane, and the device layer Is a semiconductor device having a striped surface form extending substantially parallel to the one direction. 5. The one direction is <1-100 of a zone axis.
The semiconductor element according to claim 4, wherein the semiconductor element has a> direction. 6. The semiconductor device according to claim 4, wherein the off angle is 1 ° or more and 10 ° or less. 7. The semiconductor device according to claim 4, wherein the semiconductor device is a laser device. 8. The semiconductor device according to claim 7, wherein the laser device has a resonator formed substantially parallel to the one direction. 9. The semiconductor device according to claim 8, wherein the off angle is 1 ° or more and 10 ° or less, and an end face of the resonator is formed by cleavage. 10. The semiconductor device according to claim 4, wherein the semiconductor device is a light emitting diode device.