JPH07249795A - Semiconductor device - Google Patents

Abstract

PURPOSE:To realize a high luminance short wavelength semiconductor light emitting element by growing a high quality AlGaInN based thin film with high reproducibility on a saphire substrate. CONSTITUTION:The semiconductor light emitting element comprises a plurality of semiconductor layers of AlGaInN based material laminated through buffer layers on a saphire substrate 10 wherein the buffer layer comprises a first porous AlN butter layer 11 for polarity control and nucleus formation formed sparcely (granularly) by 10nm or less on the surface of the substrate 10, and a second InN buffer layer 12 for relaxing thermal stress formed thicker than the first buffer layer 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device using an AlGaInN-based material, and more particularly to a semiconductor device having an improved buffer layer provided between a substrate and a semiconductor laminated structure for producing the device.

[0002]

2. Description of the Related Art GaN, which is one of III-V group compound semiconductors containing nitrogen, has a large band gap of 3.4 eV,
Further, it is a direct transition type and is expected as a material for a short wavelength light emitting device. In this material system, since there is no good substrate that is lattice-matched, it often grows on a sapphire substrate. However, sapphire and GaN have a large lattice mismatch of about 15%, so that they easily grow like islands. Furthermore, if the film thickness is increased in order to grow a good quality GaN layer, dislocations increase and cracks are generated during cooling due to the difference in thermal expansion between the sapphire substrate and GaN (or AlGaInN), so that a high quality film is grown. It was difficult to do.

On the other hand, in order to mitigate the effect of lattice mismatch, a very thin film of amorphous or polycrystalline AlN or GaN is formed as a buffer layer on the sapphire substrate by low temperature growth, and then a GaN layer is formed thereon. It is known how to do it. At this time, the amorphous or polycrystalline buffer layer alleviates thermal strain, and the microcrystals contained in the buffer layer become seed crystals whose orientation is aligned at a high temperature of 1000 ° C., which improves the crystal quality of the GaN layer. Has been.

When this method is used, the quality of the crystal represented by the half width of X-ray diffraction largely depends on the growth conditions of the buffer layer. That is, when the buffer layer is thick, the crystal quality is deteriorated because the orientation of the seed crystal that serves as a growth nucleus is disturbed. On the other hand, the full width at half maximum decreases as the thickness of the buffer layer becomes thinner, but if it is too thin, the function of the buffer layer is completely lost and the surface state of the crystal deteriorates sharply. That is, the growth conditions of the buffer layer are severely limited, and the crystal quality is not sufficient.

[0005]

As described above, conventionally, it is difficult to grow a crystal of a high quality AlGaInN thin film on a sapphire substrate. Furthermore, even if an amorphous or polycrystalline buffer layer is used, the growth conditions of the buffer layer are severely limited and AlG formed on the buffer layer
The crystal quality of the aInN-based thin film cannot be said to be sufficient. Therefore, it has been difficult to realize a high-luminance short-wavelength semiconductor light emitting device using an AlGaInN-based material.

The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to form a high-quality AlGaInN-based thin film with good reproducibility on a substrate that is not lattice-matched. It is an object of the present invention to provide a semiconductor device that can realize a brightness short wavelength semiconductor light emitting device.

[0007]

In order to solve the above problems, the present invention employs the following configurations.
That is, the first invention of the present application is a semiconductor device in which a semiconductor layer made of an AlGaInN-based material is laminated on a single crystal substrate with a buffer layer interposed therebetween, wherein the buffer layer is made of AlGa.
It is characterized in that it is made of an InN-based material and is formed in a porous state on the substrate surface.

Here, the following are preferred embodiments of the present invention. (1) The buffer layer is formed extremely thinly and sparsely on the substrate surface (granular), and the average film thickness is less than 10 nm. (2) The buffer layer should be AlN. (3) The single crystal substrate is a sapphire substrate, preferably the c-plane of the sapphire substrate. (4) The semiconductor layer formed on the buffer layer has a double hetero structure in which an active layer is sandwiched by p-type and n-type cladding layers to form a light emitting diode. (5) The growth temperature of the buffer layer is 350 to 800 ° C, more preferably 500 to 700 ° C. (6) The temperature rising process from the formation of the buffer layer to the start of growth of the semiconductor layer for device formation is performed in a hydrogen atmosphere containing no ammonia.

A second invention of the present application is a semiconductor device in which a semiconductor layer made of an AlGaInN-based material is laminated on a single crystal substrate via a buffer layer, and the buffer layer is made of an AlGaInN-based material. It has a laminated structure of a first buffer layer formed porous on the surface and a second buffer layer having a band gap narrower than that of the first buffer layer and thicker than that of the first buffer layer. Characterize.

Preferred embodiments of the present invention are as follows. (1) The first buffer layer is formed so as to be extremely thin and sparse on the surface of the substrate (is granular), and has an average film thickness of less than 10 nm. (2) The first buffer layer is AlN and the second buffer layer is InN or GaInN. (3) Forming a cap layer on the second buffer layer to prevent evaporation of In in the buffer layer. (4) The single crystal substrate is a sapphire substrate, preferably the c-plane of the sapphire substrate. (5) The growth temperature of the buffer layer is 350 to 800 ° C, more preferably 500 to 700 ° C. (6) The semiconductor layer formed on the buffer layer has a double hetero structure in which an active layer is sandwiched by p-type and n-type cladding layers to form a light emitting diode. (7) The temperature rising process from the formation of the buffer layer to the start of growth of the semiconductor layer for device formation is performed in a hydrogen atmosphere containing no ammonia.

According to the research conducted by the present inventors, it is essential that the role of the buffer layer is the growth nucleation for controlling the polarity of the growth surface, in addition to the lattice mismatch relaxation conventionally considered. There was found. That is, when a GaN layer is directly grown on a sapphire substrate without a buffer layer, the substrate crystal and the nitrogen source react with each other, and sapphire has a nonpolar crystal structure, so the polarity of the product nitride is disturbed. It becomes a thing.

On the other hand, when the substrate temperature is 700 ° C. or lower,
The growth plane is controlled to the A plane where the group III atoms are generated because the raw material molecule or its decomposition product that acts as the nitrogen supply source of the group V element effectively stays on the surface and the N atomic plane is first formed. Therefore, for example, when ammonia having a low decomposition rate is used as the N raw material, the formation of the N atomic plane (B plane), which becomes unstable due to the shortage of the N raw material, is suppressed. This is considered to be a major reason for the crystal quality improvement by the low temperature growth buffer layer.

Therefore, the formation of growth nuclei for controlling the polarity of the growth surface is important as the role of the buffer layer, and the growth nuclei that act in this way do not have to exist as a film, but rather are formed sparsely on the substrate surface. It is considered that the crystal quality is improved by increasing the thickness of the buffer layer regardless of the growth conditions and thickness of the buffer layer. This is because GaN is unlikely to form growth nuclei on the surface of the sapphire substrate at a substrate temperature of usually 800 ° C. or higher, so that GaN grows laterally along the substrate surface from the growth nuclei formed in advance at a low temperature. It is considered that there are almost no crystal defects due to lattice mismatch in the region grown from one growth nucleus.

Conventionally, it is considered that the rapid deterioration of crystal quality that occurs when the buffer layer is thin is caused by the fact that the substrate directly reacts with the nitrogen raw material to form a part with disordered polarity.
Specifically, when a GaN layer for forming a semiconductor element is grown on a sapphire substrate via an AlN buffer layer, the buffer layer is grown by supplying a group III source material (TMA) and a group V source material (NH ₃ ). Then, the supply of the group III raw material is stopped, the temperature is raised to a predetermined temperature, and then another group III raw material (T
MG) is supplied to start the growth of the GaN layer. At this time, since the group V raw material is still being supplied, if the buffer layer is thin, the substrate directly reacts with ammonia during the temperature rising process.

On the other hand, if the temperature is raised in an atmosphere containing no ammonia or containing only a trace amount of nitrogen raw material for preventing desorption of nitrogen element, nucleation can be performed without nitriding the substrate surface. . However, in this case, after the temperature rises, gases such as hydrogen and ammonia, which have greatly different thermal properties, are switched, and the thermal properties of the atmospheric gas change, which causes a problem that the surface temperature of the substrate changes. . In order to suppress this, the present inventors have found that it is important to carry out the growth under a reduced pressure of 70 Torr or less, preferably 40 Torr or less, at which the thermal conductivity of the gas sharply decreases.

FIG. 9 shows the relationship between the AlN buffer layer thickness when the temperature is raised in hydrogen and the X-ray diffraction half width of the GaN layer grown thereon. Buffer layer thickness less than 10nm 3
When the thickness is up to 8 nm, a much higher quality epitaxial layer than the conventional one is obtained. At this time, the buffer layer does not have a perfect film shape, but has AlN fine crystals sparsely formed and has a porous shape. Here, obtaining a high-quality epitaxial layer even if the thickness of the buffer layer is thinner than 10 nm means that the growth conditions of the buffer layer are lenient, which leads to an improvement in productivity.

When the porous buffer layer is formed in this way, the layer grown on the exposed substrate surface grows from small nuclei, so that lateral growth is promoted and a layer with few defects can be grown. Conceivable. In order to further promote the lateral crystal growth, it is best to use the sapphire c-plane for the substrate. When a substrate having a variation in plane orientation or a surface defect is used, a substrate inclined from the c-plane to the a-plane by 0.5 ° to 10 ° (preferably 1 ° to 5 °) is effective. By using the inclined substrate, it is possible to form a higher quality film.

Here, the interval between the AlN microcrystals serving as growth nuclei is determined by the growth temperature and becomes wider as the temperature rises. In order to prevent lateral growth from being alienated, it is desirable to use a high temperature at which the distance between the growth nuclei is wide. However, the growth temperature of the buffer layer is limited because the polarity of the growth nuclei is disturbed in high temperature growth. Good results were obtained from 350 ° C to 800 ° C
Range, and preferably 500 ° C to 700 ° C.

Even if this method is used, good quality GaN is obtained.
When the film thickness is increased to grow the layer, the growth temperature of GaN is as high as about 1000 ° C., so dislocations increase or cracks occur during cooling due to the difference in thermal expansion between the sapphire substrate and GaN (or AlGaInN). . Therefore, in order to relax the thermal strain, it is necessary to thicken the buffer layer and simultaneously lower the growth temperature to reduce the strain due to the temperature difference. However, if the thickness of the first buffer layer for forming the growth nuclei is increased, the orientation of the seed crystal serving as the growth nuclei is disturbed, and the crystal quality is deteriorated. Therefore, in the present invention, it is effective to stack a second buffer layer for relaxing thermal strain on the first buffer layer for forming growth nuclei.

The buffer layer for alleviating thermal strain does not necessarily have to be amorphous or polycrystalline. Therefore, a material containing In as a constituent element, which has been considered to be easily single-crystallized due to its low crystallization temperature, can be used as the second buffer layer. That is, In has a weak bond with N and A
Since it has flexibility with respect to 1N, the buffer layer containing In as a constituent element can effectively relax strain. In addition to the material containing In as a constituent element, a material having a wider bandgap than that of the first buffer layer is generally used for the second buffer layer, because the material generally has good flexibility, and thus is not particularly limited. Is possible. In this case, since a buffer layer close to a single crystal is used, the film thickness can be increased, which is more effective.

The thickness of the second buffer layer for relaxing the thermal strain is effective in a wide range of 50 nm to 1000 nm, and the In composition is easy to grow from 10% to 90%.
It is time for In order to grow a material containing a large amount of In as a constituent element as a buffer layer, In has a large surface mobility and can be formed in a wide temperature range from 300 ° C. to 1100 ° C. It is desirable to pre-grow fewer layers.

As described above, since a small growth nucleus is formed in the first buffer layer for nucleation, a material having a wide band gap, for example, a large Al composition is effective, and the second buffer for relaxing thermal strain is effective. As the layer, a material having a narrow band gap, for example, a material having a large In composition is effective. Also,
When an element structure made of a GaN-based material is formed on the second buffer layer for relaxing the thermal strain, a cap layer containing no In, such as GaN, AlN, or AlGaN, is formed in order to prevent the desorption of In. Desorption is not rapid 500
It is desirable to pre-form it in the substrate temperature range of ℃ to 800 ℃. The thickness of this cap layer is 50 nm to 1000 nm.
It may be in the range of nm.

In the present invention, the buffer layer means a film-like or granular crystal layer for the purpose of nucleation, polarity control, thermal strain relaxation and the like. As described above, according to the present invention, by forming a porous buffer layer such as AlN on a single crystal substrate such as sapphire, AlN microcrystals are sparsely formed on the substrate. This serves as a nucleus for lateral epitaxial growth of the semiconductor layer. In addition, the reaction between the substrate surface and nitrogen is prevented by increasing the temperature after the formation of the buffer layer until the start of growth of a plurality of semiconductor layers for semiconductor element formation, by performing, for example, a hydrogen atmosphere containing no ammonia. It is possible to prevent the disorder of the polarity on the substrate surface. Therefore, it is possible to improve the crystal quality and reproducibility of a plurality of semiconductor layers formed on the buffer layer. As a result, it is possible to grow a low-defect AlGaInN layer and realize a high-luminance short-wavelength light emitting device. Becomes

Further, In is formed on the first buffer layer of AlN or the like.
By forming the second buffer layer of N, GaInN, or the like, the second buffer layer functions as a thermal strain relaxation layer, which is more effective in improving the crystal quality of the plurality of semiconductor layers formed on the buffer layer.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing an element structure of a blue light emitting diode according to a first embodiment of the present invention. That is, the AlN first buffer layer 11 (9n) for forming growth nuclei and controlling the polarity on the c-plane of the sapphire substrate (single crystal substrate) 10.
m) is grown and formed at 580 ° C., and the InN second buffer layer 12 (0.5 μm) for thermal strain relaxation is further formed at 500 ° C.
The GaN cap layer 13 (0.1 μm) for preventing evaporation of In is grown and formed thereon.

After each of these layers 11 to 13 is formed, the temperature is raised to 1050 ° C. and Ga for crystal defect reduction is formed.
_0.7 In _0.3 N defect reduction layer 14 (3.0 μm), Si-doped n-type Al _0.2 Ga _0.5 In acting as an element
_0.35 N clad layer (1.0 μm) 15, Ga _0.7 In
_0.3 N active layer (0.5 μm) 16, Mg-doped p-type Al _0.2 Ga _0.5 In _0.35 N clad layer (1.0 μm)
17, Mg-doped p-type GaN contact layer (0.5 μ
m) 18 are sequentially formed.

Then, Au / Cr / Pd is formed as the p-side electrode 21 on the contact layer 18, and the defect reduction layer 1
Au / AuGe is formed as an n-side electrode 22 on the electrode 4.

In such a structure, the AlN first buffer layer 11 is sparsely and granularly formed on the substrate 10 and becomes porous, which is effective when the AlGaInN-based semiconductor layer is grown for subsequent device fabrication. Become a growth nucleus. Furthermore, In
The N second buffer layer 12 functions as a thermal strain relaxation layer, and Al
Generation of dislocations and cracks due to the difference in thermal expansion between the GaInN-based semiconductor layer and the substrate 10 can be prevented in advance. That is, a high-quality AlGaInN-based semiconductor layer can be formed by the action of the two buffer layers 11 and 12,
It is possible to realize a high-luminance short-wavelength light emitting diode.

In FIG. 2, the bandgap of the active layer 16 is changed to change the emission wavelength. FIG. 2A is an example of a green light emitting diode, and the composition of the defect reduction layer 14 'is G
a _0.5 In _0.5 N, the composition of the cladding layers 15 'and 17' is Al _0.2 Ga _0.25 In _0.55 N, and the composition of the active layer 16 'is G.
a _0.5 In _0.5 N. FIG. 2B is an example of a red light emitting diode, and the composition of the defect reduction layer 14 ″ is Ga.
_0.3 In _0.7 N, the composition of the cladding layers 15 ″ and 17 ″ is A
l _0.2 Ga _0.05 In _0.75 N, the composition of the active layer 16 ″ is Ga
_0.3 In _0.7 N.

FIG. 3A shows an example in which a Ga _0.5 In _0.5 N mixed crystal is used as the second buffer layer 32 for relaxing the thermal strain, and AlGaN is used as the cap layer 33. Further, in this case, the first buffer layer 11 for nucleation may be omitted, and FIG. 3B shows such an example. Other mixed crystals such as Al _0.5 In _0.5 N mixed crystal can be similarly used as the buffer layer 32 for relaxing the thermal strain. Second for thermal strain relief
When a mixed crystal is used as the buffer layer 32, the evaporation of In is slow, so the cap layer 33 for preventing In evaporation may be omitted. FIG. 3C shows such an example.

FIG. 4 is a schematic configuration diagram showing a growth apparatus used for manufacturing the device of this embodiment. In the figure, reference numeral 41 is a quartz reaction tube, and a raw material mixed gas is introduced into the reaction tube 41 from a gas introduction port 42. The gas in the reaction tube 41 is exhausted from the gas exhaust port 43.

A susceptor 44 made of carbon is arranged in the reaction tube 41, and the sample substrate 47 is the susceptor 4
4. Further, the susceptor 44 is induction-heated by the high frequency coil 45. The temperature of the substrate 47 is measured by the illustrated thermocouple 46 and controlled by another device.

Next, a method of manufacturing a light emitting diode using the growth apparatus of FIG. 4 will be described. First, the sample substrate 47
The (sapphire substrate 10) is placed on the susceptor 44.
1 liter of high-purity hydrogen is introduced from the gas inlet 42 per minute to replace the atmosphere in the reaction tube 41. Next, the gas exhaust port 43 is connected to a rotary pump, the pressure inside the reaction tube 41 is reduced, and the internal pressure is set within the range of 20 to 70 Torr.

Next, the substrate 47 is heated in hydrogen at 1100 ° C. to clean the surface. Next, the substrate temperature is set to 450-
After the temperature was lowered to 900 ° C., H ₂ gas was replaced with NH ₃ gas and N ₂ gas.
Organic compounds containing H ₄ gas or N, for example (CH ₃ ) ₂
While switching to N ₂ H ₂ , an organometallic Ga compound,
For example, Ga (CH ₃ ) ₃ or Ga (C ₂ H ₅ ) ₃ is introduced to grow. At the same time, organometallic Al compounds such as Al (CH ₃ ) ₃ or Al (C ₂ H ₅ ) ₃ and organometallic In compounds such as In (CH ₃ ) ₃ or In (C ₂
H ₅ ) ₃ is introduced to add Al and In.

When doping is performed, a doping raw material is also introduced at the same time. As the doping raw material, Si hydride for n-type, for example, SiH ₄ or organometallic S
i compounds such as Si (CH ₃ ) ₄ and organometallic Mg compounds for p-type such as Cp ₂ Mg or organometallic Zn
(CH ₃ ) ₂ etc. are used. When forming a layer containing In to improve the rate of incorporation of In, nitrogen, A
(CH ₃ ) ₂ N ₂ H ₂ having a higher decomposition rate than ammonia is used as a raw material, which is grown in an atmosphere containing no hydrogen such as r.

In order to increase the activation rate of the p-type dopant, it is important to suppress the incorporation of hydrogen into the crystal. Therefore, from the growth temperature to 850 ° C to 700 ° C, cooling is performed in ammonia in order to suppress dissociation of nitrogen,
If the temperature is lower than that, cooling is performed in an inert gas in order to prevent hydrogen from being mixed in the cooling process. Further, when it is necessary to increase the activation rate of the p-type dopant, heat treatment is performed in nitrogen radicals generated by RF plasma. this is,
Desorption of nitrogen atoms from the crystal can be completely prevented 900 ° C
This is because not only the heat treatment at a high temperature of 1 to 1200 ° C. is possible, but also crystal defects such as nitrogen vacancies can be removed.

Specifically, 1 × 10 ₃ of NH ₃ is used as a raw material.
^-3 mol / min, Ga (CH ₃ ) ₃ 11 × 10 ^-5 mol / mi
Growth is performed by introducing n and Al (CH ₃ ) ₃ at 1 × 10 ^-6 mol / min. Substrate temperature is 1050 ° C., pressure is 38 Torr, total flow rate of source gas is 1 l / min, and n-type S is used as dopant.
Mg is used for the i and p types. Si (CH ₃ ) as raw material
₄ , Cp ₂ Mg is used.

When the wafer thus obtained was evaluated by X-ray diffraction, crystal defects were dramatically reduced, and it was expected that a high-luminance short-wavelength light-emitting device could be realized. In addition, the wafer is heated to 400 to 1100 ° C. (preferably 700 to 10) in a nitrogen radical.
By annealing at 00 ° C., it is possible to suppress the escape of N during annealing and further reduce the resistance of the p-type layer. FIG. 10 shows a schematic view of an annealing device. In addition,
In the figure, 91 is a reaction tube, 92 is a wafer, 93 is a susceptor also serving as a heater, 94 is a high frequency coil for activating gas, and 95 is a high frequency power supply.

It is also effective to perform annealing with a nitrogen-containing compound that does not release active hydrogen. Specifically, annealing in an organic compound having an azide group, for example, ethyl azide also suppresses escape of N during annealing, and since H is not taken in, the p-type layer can have a lower resistance. (Embodiment 2) FIG. 5 is a sectional view showing an element structure of a light emitting diode according to a second embodiment of the present invention. In this embodiment, the efficiency is further improved by providing the contact layer not only on the p side but also on the n side.

An AlN first buffer layer 51 (9 nm) for growth nucleation and polarity control is grown and formed at 350 ° C. on the c-plane of the sapphire substrate 50, and Ga for thermal strain relaxation is further formed.
_0.5 In _0.5 N Second buffer layer 52 (0.5 μm) is 5
It is grown and formed at 50 ℃, and on top of it G
The aN cap layer 53 (0.1 μm) is grown and formed at 650 ° C.

After these layers 51 to 53 are formed, the temperature is raised to 1050 ° C., the Se or S-doped n-type GaN contact layer 54 (2.0 μm), and the Se or S-doped GaInN for lattice mismatch relaxation. (GaN ~
Ga _0.7 In _0.3 N) composition grading layer 55 (1.
0 μm), and further Se or S-doped Ga _0.7 In _0.3 N defect reduction layer 56 (4.0 μm) for crystal defect reduction,
Se or S-doped (1 × 10 ¹⁸
cm ⁻³ ) n-type Al _0.1 Ga _0.55 In _0.35 N cladding layer 57 (1.0 μm), Ga _0.7 In _0.3 N active layer 58
(0.5 μm), Mg or Zn doped (1 × 10 ¹⁸
cm ⁻³ ) p-type Al _0.1 Ga _0.55 In _0.35 N cladding layer 59 (1.0 μm), Mg or Zn doped (5 × 1)
0 ¹⁸ cm ⁻³ ) p-type GaN contact layer 60 (0.5 ^μm )
m) are sequentially grown and formed.

Then, Pd: 5 is formed on the contact layer 60.
00 nm, Cr: 100 nm, Au: 500 nm, and AuGe: 100 nm, Au: 5 on the contact layer 54.
After the thickness of 00 nm is formed, it is heat-treated at 400 to 800 ° C. in an inert gas or N ₂ to form ohmic electrodes (p-side electrode 61, n-side electrode 62).

Even with such a structure, the AlN first buffer layer 51 and the GaInN second buffer layer 12 serve to form a high-quality AlGaInN semiconductor layer, which is the same as in the first embodiment. The effect of is obtained.
Further, in this embodiment, since the lattice mismatch between the active layer 58 and the cladding layers 57 and 59 is 0.3%, the emission wavelength becomes longer and the absorption can be reduced.

In the present embodiment, the composition grading layer 55 is provided to alleviate the lattice mismatch, but it is not always necessary to use grading. In addition, not only GaInN but also GaN can be used as the thermal strain relaxation layer,
FIG. 6 is such an example. Here, the sapphire substrate 5
An AlN first buffer layer 51 (9 nm) for growth nucleus formation and polarity control was grown and formed on the c-plane of 0 at 350 ° C., and a GaN second buffer layer 72 (0.5) for thermal strain relaxation was formed.
μm) is grown and formed at 550 ° C. Then, the respective layers 54 to 60 are grown and formed thereon similarly to FIG.

Further, the buffer layer for alleviating the thermal strain may be omitted, and FIG. 7 shows such an example. Sapphire c
A granular AlN first buffer layer 51 (average film thickness: 5 nm) for growth nucleus formation and polarity control is formed at 400 ° C. on a substrate 50 which is off by 5 ° in the a direction from the surface. Then, the respective layers 54 to 60 are grown and formed thereon similarly to FIG.

In order to form growth nuclei, it is preferable that the grains are formed as sparsely as possible so that lateral growth is promoted and a high quality layer is formed. In addition, when growing on the a-plane, a stripe pattern was often observed on the growth surface, but by adopting the granular buffer layer, mirror growth became possible. Further, GaN may be used as the buffer layer for forming the growth nuclei, and in this case, nitrogen dissociation can be suppressed by introducing an extremely small amount of ammonia to the limit of GaN growth.

FIG. 8 shows the relationship between the ammonia flow rate and the growth rate during the growth of GaN, which is 2% of the total flow rate (1 l / min).
Even if the amount of ammonia is reduced to 1/00, GaN grows, and the film thickness becomes maximum at about 1/50 of the total flow rate.
Therefore, when 1/50 to 1/200 of the total flow rate of ammonia is introduced, the dissociation of nitrogen is most suppressed, and under such conditions, G is used as a buffer layer for forming growth nuclei.
aN can be used.

The present invention is not limited to the above embodiments. The element structure is not limited to those described in the embodiments, and can be changed as appropriate. In short, the present invention can be applied to a case where a semiconductor layer made of an AlGaInN-based material is formed on a single crystal substrate to form a light emitting element or the like. Further, the substrate is not necessarily limited to the sapphire substrate, and SiC or other single crystal can be used. Further, the present invention is not necessarily limited to the light emitting element, and can be applied to, for example, a high temperature operating semiconductor element. In addition, various modifications can be made without departing from the scope of the present invention.

[0049]

As described above in detail, according to the present invention, A
It is possible to improve the crystal quality and reproducibility of a semiconductor layer for forming a device made of a 1GaInN-based material, and as a result, it is possible to grow a low-defect AlGaInN-based semiconductor layer, which is suitable for high-luminance short-wavelength light-emitting devices and the like. Realization is possible.

[Brief description of drawings]

FIG. 1 is a sectional view showing an element structure of a blue light emitting diode according to a first embodiment.

FIG. 2 is a sectional view showing a modification of the first embodiment.

FIG. 3 is a sectional view showing another modification of the first embodiment.

FIG. 4 is a schematic configuration diagram showing a growth apparatus used for manufacturing the device of the example.

FIG. 5 is a sectional view showing an element structure of a light emitting diode according to a second embodiment.

FIG. 6 is a sectional view showing a modification of the second embodiment.

FIG. 7 is a sectional view showing a modification of the second embodiment.

FIG. 8 is a characteristic diagram showing the relationship between the ammonia flow rate and the growth rate when growing GaN.

FIG. 9 is a characteristic diagram showing the relationship between the AlN buffer layer thickness and the X-ray diffraction half-value width of the GaN layer.

FIG. 10 is a schematic configuration diagram showing an annealing device used in Examples.

[Explanation of symbols]

 10, 50 ... Sapphire substrate (single crystal substrate) 11, 51 ... AlN first buffer layer 12 ... InN second buffer layer 13, 53 ... GaN cap layer 14, 56 ... GaInN defect reduction layer 15, 57 ... n-type AlGaInN clad Layers 16, 58 ... n-type GaInN active layer 17, 59 ... p-type AlGaInN cladding layer 18, 60 ... p-type GaN contact layer 21, 22, 61, 62 ... electrode 32 ... GaInN buffer layer 33 ... AlGaN cap layer 52 ... GaInN Second buffer layer 54 ... n-type GaN contact layer 55 ... n-type GaInN composition grading layer 72 ... GaN second buffer layer

Claims (2)

[Claims] 1. AlG on a single crystal substrate via a buffer layer.
In a semiconductor device formed by stacking a plurality of semiconductor layers made of aInN-based material, the buffer layer is made of AlGaInN-based material and is formed on the surface of the substrate in a porous form for polarity control and nucleation. A semiconductor device characterized by being present. 2. AlG on a single crystal substrate via a buffer layer.
In a semiconductor device formed by stacking a plurality of semiconductor layers made of an aInN-based material, the buffer layer is made of an AlGaInN-based material and is formed on the surface of the substrate in a porous form to provide a first buffer layer for polarity control and nucleation. And a second buffer layer made of AlGaInN-based material and formed on the first buffer layer to be thicker than the buffer layer for relaxing thermal strain.