JPH06326416A - Compound semiconductor element - Google Patents

Abstract

PURPOSE:To accomplish high efficiency of a semiconductor element by providing a cubic crystal SiC substrate and a GaxAlxIn1-x-yN (0<=x<=1, 0<=y<=1) layer. CONSTITUTION:A GaN buffer layer 2 of 1mum in thickness, a clad layer 3 consisting of p-GaAlInN of 1mum in thickness, a light-emitting layer 4 consisting of undoped GaAlInN of 0.1mum in thickness, are formed successively on a 3C-SiC substrate 1, and a semiconductor layer is composed of the above-mentioned layers. As the clad layer 5, consisted of final GaAlInN, is formed in N-type in this semiconductor laser, the taking-in of hydrogen into the p-GaAlInN clad layer 3 can be prevented, and a low resistance p-GaAlInN clad layer 3 can be formed. As a result, a high brightness short wavelength light-emitting element can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor device.

[0002]

2. Description of the Related Art GaN, which is a III-V group compound semiconductor containing nitrogen, has a large bandgap of 3.4 eV and is a direct transition type, and is therefore expected as a material for a short wavelength light emitting device. However, since the crystal structure is wurtzite type and the ionicity is large, lattice defects are likely to occur as described below, and it is difficult to obtain a p-type crystal with low resistance. Particularly, when Mg is used as an acceptor impurity, p-type crystal is obtained. When the layer is epitaxially grown, hydrogen diffuses into the epi layer and the activation rate of the acceptor is extremely lowered, which makes it difficult to reduce the resistance.

That is, from before, for example, GaN is used as a light emitting layer,
A double-hetero laser structure using GaAlN as a cladding layer has been prototyped. In this case, the thickness of the cladding layer required to confine light in the light emitting layer depends on the wavelength.
Since aN has a short emission wavelength, it is considered that the thickness of the clad layer may be thin, and the device is usually made of a thin clad layer of about 0.2 μm.

However, the clad layer also plays a role of confining carriers in the light emitting layer. According to the research conducted by the present inventors, for example, in the case of a heterojunction made of GaAlN and a nitride such as GaN, a heterojunction is formed at the hetero interface. Since the barrier height is low, it was found that the clad layer thickness that has been used so far is not sufficient to efficiently confine electrons and holes in the light emitting layer. However, GaN does not have a substrate that is lattice-matched with this, and when a thick film is grown, strain due to the difference in the lattice constant and the difference in the thermal expansion coefficient is accumulated. It is considered difficult to do.

Specifically, GaN often grows on a sapphire substrate having a large lattice mismatch of about 15% for convenience. However, sapphire and GaN have different crystal types and a large difference in thermal expansion coefficient. Therefore, strain at the interface due to the lattice mismatch between the substrate and GaN induces lattice defects. Therefore, various methods have hitherto been tried in order to reduce the influence of lattice mismatch.

For example, when the vapor phase epitaxial growth method (VPE method) is used as the crystal growth method, 100
Attempts have been made to alleviate the strain at the interface with the substrate by growing a thick film of about μm, but it was not possible to grow good quality crystals such as cracks. Further, it was attempted to insert an amorphous layer by low temperature growth on the substrate by the metal organic chemical vapor deposition method (MOCVD method), but the grown GaN has a wide X-ray diffraction width and still has high density defects. is doing. Attempts were also made to grow thick films in MOCVD growth, but rather defects increased.
It was impossible to grow a thick film of 3 μm or more.

On the other hand, with respect to the problem of p-type crystal resistance,
Recently, it has been reported that the resistance can be significantly reduced by irradiating GaN with an electron beam or heating it in an inert atmosphere. However, it is difficult to obtain a device having good characteristics by this method. That is, in the method of irradiating the electron beam, it is necessary to irradiate the electron with high energy in order to make the electron penetrate to a sufficient depth, and the crystal defect is easily induced. Further, in the case of heat treatment, it is necessary to remove hydrogen taken in the epi layer to realize a sufficiently low resistance.
Heating at 0 ° C. or higher is required, but at this temperature, vacancies are generated in the epilayer due to the release of N atoms, which leads to lattice defects.

Further, even if a p-type layer having a low resistance is obtained, the contact resistance with the electrode and the series resistance are not improved, and it is also necessary to reduce these resistances in order to improve the device performance. Becomes

[0009]

As described above, GaN
Has a high expectation as a material for a light-emitting device, but when a GaN-based compound layer is grown thick to create a device, a high density of lattice defects occurs, so that the thickness of the clad layer is limited. There is a problem that it is difficult to reduce the resistance of the mold layer and the like.

The object of the present invention is to produce high quality Ga _x Al _y I.
It is to provide a high-performance compound semiconductor device by growing n _1-xy N.

[0011]

The present invention (Claim 1) includes:
A cubic SiC substrate and (11) of this cubic SiC substrate
1) Ga _x Al _y In _1-xy N (0 ≦
x <1, 0 <y <1) layer is provided.

The present invention (claim 4) provides a substrate and a Ga _x Al _y In _1-xy N (0 ≦
x ≦ 1, 0 ≦ y ≦ 1) layer, and Ga _x Al _y
Provided is a compound semiconductor device having a pn junction, wherein the crystal plane of the In _1-xy N layer facing the substrate is an N plane.

Further, according to the present invention (claim 8), a p-type conductive substrate and a p-type Ga _x formed on the p-type conductive substrate.
An Al _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) layer;
This p-type Ga _x Al _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦
y ≦ 1) n-type Ga _x Al _y In _1-xy formed on the layer
There is provided a compound semiconductor device comprising an N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) layer.

[0014]

In general, the process of introducing defects into the growth layer is
It can be divided into two ways. One is introduced by strain due to the difference in lattice constant between the substrate and the growth layer during growth,
The other one is introduced by strain caused by the difference in thermal expansion between the substrate and the growth layer when cooling from the growth temperature to room temperature after the growth is completed. Until now, defects in the growth layer have been thought to be mainly caused by lattice distortion with the former substrate.
GaAlIn for which no suitable substrate has been found to grow
It has been considered that it is extremely difficult to obtain a growth layer having a low dislocation with an N-based material.

However, according to the research conducted by the present inventors, Ga
Since the growth temperature of N is as high as 1000 ° C. or higher, most of the dislocations are eliminated by annealing at the growth temperature, and most of the dislocations observed are accumulated strains during cooling due to the large difference in thermal expansion coefficient with the substrate. It became clear that it was caused by. This result is particularly remarkable when the growth plane is the (0001) plane (C plane), which is considered to easily move dislocations. Therefore, in the case of a GaN-based compound, it was found that it is important to use a substrate having a difference in thermal expansion rather than a lattice constant in order to reduce defects.

Since 6H-SiC has the same hexagonal crystal structure as GaN and has a close lattice constant, it has been attempted to grow a GaN layer on a 6H-SiC substrate. However, the defects in the GaN layer grown on 6H-SiC were not significantly reduced. This is probably because the difference in thermal expansion between 6H-SiC and GaN is large. However, the same S
Even in iC, the thermal expansion in the direction parallel to the (111) plane of 3C-SiC, which is a cubic crystal, and the thermal expansion of GaN in the direction parallel to the a-axis are very close.

FIG. 1 shows the temperature (T) of GaN and 3C-SiC.
The change (da) of the lattice constant with respect to is shown. In the region from the growth temperature to around 100 ° C. where the dislocation motion can be almost ignored, the strain due to the difference in thermal expansion between the GaN layer which is the epi layer and the 3C-SiC substrate is 0.001% or less, and 3C-S.
It can be seen that by using iC as the substrate, a dramatic reduction in epilayer defect density can be expected.

Although 3C-SiC is a cubic crystal and has a large lattice constant of 0.436 nm, the distance between the lattices in the (111) plane is 0.308 nm, and the lattice constant of GaN is 0.318 nm. Close to Therefore, by growing GaN on the (111) plane of 3C-SiC, it becomes possible to grow high-quality GaN with low dislocation.

Further, since the strain due to the difference in thermal expansion between the substrate and the epi layer is significantly reduced, it becomes possible to grow a thick film of 3 μm or more, and the strain caused by the difference in lattice constant is caused by performing the thick film growth. It is relaxed, allowing the growth of higher quality layers with lower dislocations. Furthermore, a high-performance semiconductor device using this epi layer can be obtained.

In particular, when a double heterojunction type light emitting device is manufactured by using such an epi layer, the cladding layer also serves to confine carriers in the light emitting layer as described above, and in the case of the nitride system, Since the height of the barrier at the hetero interface is low, a film thickness of at least 1 μm is required to more efficiently trap electrons and holes in the light emitting layer. On the other hand, GaN is formed on the (111) plane of the 3C-SiC substrate.
It is possible to realize a clad layer thickness sufficient for confining carriers by producing an element made of.
A mixed crystal of GaN and Al, In is also a nitride-based material similar to GaN, and has a coefficient of thermal expansion that hardly changes. Therefore, it is possible to grow a high-quality layer with a similarly thick film thickness.

Further, GaN and Al used in the present invention
III-V group compounds such as N and InN have a wurtz-type crystal structure, and usually have a (1000) plane which is a crystal growth plane.
There are two types of plane orientations, the A plane in which the group III element controls the property and the B plane in which the group V element controls the property. According to the research conducted by the present inventors, GaAlInN grows three-dimensionally (when the growth rate is different on the growth surface, when the growth is performed so that the A surface is on the surface on the substrate side with respect to the growth direction). However, if the growth is performed so that the B surface is located on the surface on the substrate side with respect to the growth direction, two-dimensional growth (phenomenon in which the growth surface becomes uniform) may occur and defects may occur. Has been found to decrease. Therefore, such a good GaAlInN
By using the epitaxial layer for a compound semiconductor device having a pn junction, it is possible to improve the performance of the device.

When the above-mentioned 3C-SiC is used for the substrate, as shown in FIGS. 2 (a) and 2 (b), SiC is used.
Can distinguish between the Si plane and the C plane, but in GaN, Ga corresponds to Si and N corresponds to C. Therefore, it is preferable to grow GaAlInN so that the N atoms of the B surface face the Si surface of the SiC substrate and the growth surface becomes the A surface. Therefore, specifically, for example, S having a Si surface on the surface
By growing an epitaxial layer on the iC substrate by a well-known vapor phase growth method, the polarity can be controlled so that the B-face comes to the substrate-side face.

Further, when GaN is grown on the sapphire substrate by the metal organic chemical vapor deposition method, ammonia is usually used as the nitrogen source, but the growth temperature is 1000.
At a high temperature near ℃, an AlN layer is formed on the surface of the sapphire substrate and the surface of the sapphire substrate becomes the B surface.
The growth surface of N becomes the B surface. However, when ammonia having such a low decomposition rate and a short supply of N atoms is used, the growth surface is the B surface, the state in which the N atoms are exposed is not stable, and the growth surface is the A surface. The state in which the group III element appears on the surface is stable. Therefore, Ga on the sapphire substrate
When N is directly grown, it is difficult to grow a high-quality crystal, and in order to obtain a good pn junction by suppressing the introduction of defects and growing a high-quality crystal, the crystal polarity is controlled. Then, it is important to set the growth surface to the A surface.

Here, G is formed on a non-polar substrate such as sapphire.
The polarity of the crystal when a group III-V compound such as aN is grown is determined by whether the element initially adsorbed on the substrate surface is the group III element or the group V element. When the group V element is first adsorbed, the A surface becomes the growth surface, and when the group III element is first adsorbed, the B surface becomes the growth surface. Therefore, as described above, in order to make the growth surface the A-plane, it is sufficient to adsorb the N atom that is the V-type element first, regardless of the type of the group III element. Therefore, when a sapphire substrate is used, in order to effectively stop the ammonia molecule or its decomposed product, which acts as a nitrogen supply source of the group V element, on the surface,
It is preferable to set the substrate temperature at 700 ° C. or lower, preferably 600 ° C. or lower to form the buffer layer.

In the present invention, the buffer layer for controlling the polarity described above is preferably a single crystal. What is important is that in the conventional polycrystalline and amorphous materials, it is necessary to strictly control the film thickness in order to prevent the loss of information on the crystal orientation of the substrate, and to control the polarity of the crystal. This is not possible, but the method using a single crystal buffer layer does not have such a restriction. Furthermore, when InN containing In, GaInN, AlInN, GaAlInN, or the like is used, a high-quality single crystal can be grown even at a low temperature of 600 ° C. or lower, which is particularly effective. Here, FIG.
(A), (b) is a schematic diagram which respectively shows the GaN layer which the crystal growth grown on the sapphire substrate and which has a different plane orientation. As shown in the figure, when GaN is grown directly on the substrate, the growth surface becomes the B surface, while when GaN is grown through the buffer layer, the growth surface becomes the A surface and the B surface has the N surface.
It can be seen that the atoms face each other.

As described above, in the present invention, the polarity is controlled,
By selectively growing the epitaxial layer of Ga _x Al _y In _1-xy N so that the A-plane becomes the growth surface with respect to the growth direction, dislocations and strains are drastically reduced, and Ga _{x with} low defects is formed. A
It is possible to grow an l _1-xy In _y N crystal, and it is possible to improve the performance of a compound semiconductor device having a pn junction using the crystal.

Needless to say, the compound semiconductor element having such a pn junction may have a double hetero type junction. Further, in the present invention, the polarity of the growing crystal can be determined by RBS (Razor Forward Backscattering).

Further, in the compound semiconductor device according to the present invention, first, as described above, in order to obtain a p-type layer having a low resistance,
It is known that it is necessary to increase the activation rate of the p-type dopant, and in order to increase the activation rate, it is known that it is important to reduce the incorporation of hydrogen into the crystal. That is, SIMS analysis of GaN grown by MOCVD shows that a large amount of hydrogen is mixed in, and the hydrogen reduces the activation rate of the p-type dopant.

Here, the impurities taken into the crystal are
Usually, it is often taken from the raw material during growth. However, the present inventors have revealed that hydrogen in GaN is not incorporated into crystals during growth, but is incorporated mainly by diffusion from the surface in the cooling process after growth. Therefore, if the amount of hydrogen taken into the p-type layer during the cooling process is reduced, the activation rate of the p-type dopant is increased, and the p-type layer having a low resistance can be formed.

There are several possible methods for preventing the p-type layer from being exposed to hydrogen during the cooling process. For example, since it is generally known that the diffusion rate of hydrogen is slow in the n-type layer, the n-type layer is grown as a cap layer at the final stage of growth, and the p-type layer is exposed to hydrogen during the cooling process. By preventing this, it becomes possible to suppress the incorporation of hydrogen into the p-type layer. Up to now, in the device using the GaN-based material, the n-type layer is generally formed first, and then the p-type layer is formed, and it is a practical device to grow the n-type layer as the cap layer in the final stage of the growth. Is not done in.

Although Mg is usually added in order to obtain a p-type layer of GaN, it is conventionally difficult to control the concentration and concentration profile in a low Mg concentration region.
In order to form a pn junction, it had to be added to a concentration close to the solid solution limit. However, such high concentration of Mg
Causes a rapid diffusion, so that a steep concentration profile is obtained, but the crystal quality is remarkably deteriorated, and a high-quality n-type layer cannot be grown on this.

However, according to the research conducted by the present inventors, M
It was found that g can be added with good controllability by the method of addition, and if excessive addition is not necessary, it will not precipitate on the crystal surface and roughen the surface. It is also possible to grow the mold layer. Further, if it becomes possible to grow the n-type layer on the p-type layer, as described above, the uptake of hydrogen into the p-type layer is reduced, and the activation rate of the p-type dopant is increased. Therefore, in the present invention, it is possible to realize an element structure having a high-quality n-type layer on a low-resistance p-type layer.

More specifically, before the p-type layer is grown, Mg is also added to the buffer layer in advance, and then the p-type layer is formed by doping Mg.
A type GaAlInN layer is grown, and then an n-type GaAlInN layer doped with Si is grown. This allows
Since the p-type layer is not exposed to hydrogen during the cooling process, it is possible to grow the p-type GaAlInN layer having a low resistance.

Further, by supplying a small amount of Mg raw material in advance, both good controllability and sharp concentration change can be achieved even in the low concentration region. Therefore, it is possible to control the Mg concentration to ½ or less of the maximum concentration capable of suppressing the generation of crystal defects, and it is possible to improve the performance of the device without impairing the reliability. Furthermore, even if the substrate is n-type,
By growing an n-type layer in the final layer and removing the n-type layer after cooling, it is possible to form a pn junction with a low-resistance p-type layer.

In addition to the above description, as a method for forming a p-type layer having a low resistance, it is conceivable to devise a cooling process after completion of growth. The elimination of nitrogen atoms, which reduces the quality of the growth layer,
It is small at a temperature of 900 ° C or lower, and can be almost ignored at a temperature of 700 ° C or lower. On the other hand, the penetration of hydrogen atoms, which increases the resistance of the p-type layer, starts at 800 ° C. or lower and becomes remarkable at 700 ° C. or lower. Therefore, from the growth temperature, 900-700 ℃
By cooling to a moderate temperature in an atmosphere containing nitrogen such as ammonia and cooling at a temperature lower than that in an inert gas, it is possible to prevent harmful desorption of nitrogen and invasion of hydrogen at the same time.

Unlike the method of desorbing hydrogen by post-treatment, this method does not limit the time of exposing the grown crystal to an inert gas at a high temperature, so that it can be rapidly cooled in a short time and prevents deterioration of crystal quality. It is possible to

As described above, the cooling process after the growth is completed,
By carrying out in a hydrogen-free atmosphere, it is possible to prevent nitrogen desorption and hydrogen invasion at the same time in this cooling process, and it is possible to grow a p-type GaInAlN layer of low resistance and high quality. This leads to the realization of a short-wavelength light emitting device with high brightness.

Next, the inventors of the present invention have earnestly studied to reduce the contact resistance between the low resistance p-type layer and the electrode as described above, and have obtained the following findings.

That is, since GaN is conventionally formed on a sapphire substrate and the sapphire substrate is insulating, an n-type GaN layer and a p-type Ga layer are formed on the sapphire substrate.
An N layer is grown in this order, and an exposed surface is formed on an n-type GaN layer which generally has a relatively low resistance.
An electrode was formed on the aN layer. However, as described above, considering that it is difficult to form the p-type GaN layer having a low resistance on the uppermost portion, the p-type GaN layer and the n-type GaN layer are grown in this order on the sapphire substrate, and p It is conceivable to form an exposed surface on the n-type GaN layer and form electrodes on the p-type GaN layer and the n-type GaN layer. However, p-type G
Since the aN layer has much higher resistance than the n-type GaN layer, in such a structure in which the current flows in the in-plane direction of the p-type GaN layer, the path through which the current flows in the p-type GaN layer is long, and the device series Therefore, a high-performance element cannot be obtained. Further, in any structure, p-type GaN is
The contact resistance with the electrode is high, and there is a drawback in this respect as well.

On the other hand, in the present invention, a p-type conductive substrate is used in place of the sapphire substrate, and a device structure in which a p-type GaN layer and an n-type GaN layer are grown in this order on the p-type conductive substrate is provided. As a result, all the above problems can be solved. That is, according to this element structure, the p-type layer having the n-type layer as the cap layer has a relatively low resistance, and the electrodes are simply formed on the back surface of the p-type conductive substrate and on the n-type GaN layer. Then, the problem of contact resistance between the p-type layer and the electrode is solved by the interposition of the p-type conductive substrate,
Moreover, since the current flows in the p-type layer along the film thickness direction, the path thereof is short, the serial resistance of the element is suppressed, and it is possible to realize a high brightness short wavelength light emitting element.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a schematic configuration diagram of a semiconductor laser according to an embodiment of the present invention. 1 on the 3C-SiC substrate 1
μm thick GaN buffer layer (undoped) 2, 1 μm
A cladding layer 3 made of m-thick p-GaAlInN
(Mg-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ), undoped G having a thickness of 0.1 μm
The light emitting layer 4 made of aAlInN, and n having a thickness of 1 μm
A cladding layer 5 (undoped or Si-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ) made of —GaAlInN is sequentially formed, and thereby a semiconductor laser is formed. In the figure, reference numeral 6 indicates a current blocking layer made of SiO ₂ , and reference numerals 7 and 8 indicate metal electrodes.

In this semiconductor laser, the final GaAlI
Since the cladding layer 5 made of nN is n-type, p−
It is possible to prevent hydrogen from being taken into the cladding layer 3 made of GaAlInN, and to reduce the resistance of p-GaAlInN.
It is possible to form the cladding layer 3 made of. as a result,
It is possible to realize a high brightness short wavelength light emitting device.

Further, since the cladding layers 3 and 5 made of p-type and n-type GaAlInN are formed with a thickness of 1 μm, it is possible to efficiently inject a current into the light emitting layer 4 and improve the light emitting efficiency. Can be planned.

Next, a crystal growth method adopted for manufacturing the semiconductor laser shown in FIG. 4 will be described. Figure 5
FIG. 5 is a schematic configuration diagram showing a growth apparatus used for manufacturing the semiconductor laser shown in FIG. In the growth apparatus shown in FIG. 5, the raw material mixed gas is introduced into the reaction tube 11 through the gas introduction port 12. Then, the gas in the reaction tube 11 is exhausted from the gas exhaust port 13. A carbon susceptor 14 is arranged in the reaction tube 11, and a sample substrate 15
Are placed on this susceptor 14. Also, the susceptor 1
4 is induction-heated by the high frequency coil 16.

First, the SiC substrate having the (111) plane is placed as the sample substrate 15 on the susceptor 14. High-purity hydrogen is introduced from the gas introduction pipe 12 at a flow rate of 1 liter / min to replace the atmosphere in the reaction pipe 11. Next, the gas exhaust port 13 was connected to a rotary pump, the inside of the reaction tube 11 was exhausted to reduce the pressure, and the internal pressure was adjusted to 20-300 torr.
Set to the range of.

Next, after setting the substrate temperature to 450 to 900 ° C., an organometallic Al compound, an organometallic Ga compound, and an organometallic In are used together with NH ₃ gas as an N source.
A compound is introduced and crystal growth is performed. Organometallic A
Examples of the l compound include Al (CH ₃ ) ₃ or Al
(C ₂ H _{5) 3,} the organometallic Ga compound, for example, Ga (CH _{3) 3} or Ga (C ₂ H _{5) 3,} as the organometallic In compound, for example, In (CH _{3) 3} or In
As (C ₂ H ₅ ) ₃ and N raw materials, in addition to NH ₃ gas,
For example, N ₂ H ₄ , CH _{3 2} N ₃ , (CH ₃ ) ₂ NH ₂ ,
C ₂ H ₅ N ₃ can be used.

At this time, when doping is performed, a doping raw material is also introduced at the same time. As a doping raw material, Si hydride such as SiH ₄ for n-type, S
Organometallic Si compounds such as i (CH ₃ ) ₄ , H ₂ Se
The above Se hydride and the organometallic Se compound such as Se (CH ₃ ) ₂ can be used. In addition, organometallic Mg compounds such as Cp ₂ Mg (cyclopentadienyl magnesium), MCp ₂ Mg (methylcyclopentadienyl magnesium), i-PrCp ₃ Mg (isopropylcyclopentadienyl magnesium) for p-type, An organometallic Zn compound such as Zn (CH ₃ ) ₂ can be used.

Specifically, in manufacturing the semiconductor laser shown in FIG. 4, 1 × 10 ⁻³ mol / mi of NH ₃ is used as a raw material.
n, Ga (C ₂ H ₅ ) ₃ at 1 × 10 ⁻⁵ mol / min,
In (CH ₃ ) ₃ at 1 × 10 ⁻⁶ mol / min, Al
(CH ₃ ) ₃ was introduced at a flow rate of 1 × 10 ⁻⁶ mol / min for growth. Substrate temperature is 700 ° C, pressure is 75t
The total flow rate of orr and the raw material gas was 1 liter / min. As the dopant, Si was used as the n-type dopant and Mg was used as the p-type dopant. Si is silane (SiH ₄ )
, Mg is cyclopentadienyl magnesium (Cp ₂
Mg) was mixed in the source gas to dope.

When the semiconductor laser wafer thus obtained was cleaved to form a laser element having a cavity length of 300 μm, blue light laser oscillation was confirmed by a pulse operation with a pulse width of 100 μsec at a liquid nitrogen temperature.

In this embodiment, G is used as the buffer layer.
Although aN was used, p-type GaAlN or p-type GaAlI was used.
You may grow nN.

FIG. 6 is a schematic configuration diagram of an LED according to another embodiment of the present invention. P-Ga on the 3C-SiC substrate 21
N buffer layer (10 μm) 22, p-GaInAlN layer (2 μm) 23, n-GaInAlN (2 μm) layer 24
Are sequentially formed. In the figure, reference numerals 25 and 26 both denote metal electrodes.

The LED shown in FIG. 6 can be manufactured by using the growth apparatus shown in FIG. 5 in the same manner as in the case of manufacturing the semiconductor laser device shown in FIG.

FIG. 7 shows an LED chip 3 according to this embodiment.
1 shows a state in which 1 is embedded in a resin case 32 which also serves as a lens. Reference numeral 33 indicates an internal lead, and 34 indicates an external lead. About the LED embedded in the resin case shown in FIG. 5, blue light emission of about 5 mcd was confirmed.

FIG. 8 is a schematic configuration diagram of a semiconductor laser according to another embodiment of the present invention. A GaN buffer layer (undoped) 42 having a thickness of 1 μm is formed on a 3C-SiC substrate 41, and a cladding layer 43 (undoped or Si-doped, 1 × 10 ^{16) made} of n-GaAlInN is formed thereon.
1 × 10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ) is 1 μm
Of undoped GaAlInN on top of which
Is formed to a thickness of 0.1 μm, and a cladding layer 45 made of p-GaAlInN is further formed thereon.
(Mg-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1
× 10 ¹⁷ cm ⁻³ ) is formed with a thickness of 1 μm. In the figure, reference numeral 46 is a current blocking layer made of SiO ₂ , 4
Reference numerals 7 and 48 denote metal electrodes, respectively.

In this semiconductor laser, p-type and n-type GaAlIn, which are clad layers, are provided via a GaN buffer layer.
Since the N layer can be formed to a thickness of 1 μm, current can be efficiently injected into the light emitting layer, and the light emitting efficiency can be improved. In this semiconductor laser, n-type GaAlIn is formed on the p-GaAlInN layer.
By forming the N layer, cooling and then removing the n-type layer, hydrogen can be prevented from being taken into the p-GaAlInN layer, and a low-resistance p-GaAlInN layer can be formed. As a result, a high-luminance short-wavelength semiconductor laser can be realized.

FIG. 9 is a schematic configuration diagram of a semiconductor laser according to still another embodiment of the present invention. 3 out of (111) plane
A GaN buffer layer 52 (undoped) having a thickness of 1 μm is formed on a C-SiC substrate 51, and p-GaA is formed thereon.
clad layer 53 made of lInN (Mg-doped, 1 × 1
0 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ) is formed to a thickness of 1 μm, and undoped GaAl is formed thereon.
A light emitting layer 54 made of InN is formed to a thickness of 0.1 μm, and a cladding layer 5 made of n-GaAlInN is formed thereon.
5 (undoped or Si-doped, 1 × 10 ¹⁶ to 1 ×
10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ) is formed to a thickness of 1 μm, and a current blocking layer 56 made of p-GaAlInN and a cap layer 57 made of n-GaAlInN are formed thereon. . Reference numerals 58 and 59 denote metal electrodes.

In the semiconductor laser according to this example, 3C
Since the GaN buffer layer is formed on the (111) plane of the -SiC substrate, it is possible to grow high-quality GaN with low dislocation. In addition, p-type and n-type G that are cladding layers
Since the aAlInN layer is formed to have a thickness of 1 μm, current can be efficiently injected into the light emitting layer, and the light emitting efficiency can be improved.

A case where the semiconductor laser according to this embodiment is grown using the growth apparatus shown in FIG. 5 will be described below.

First, the 3C-SiC substrate having the (111) plane is placed on the susceptor 14. High-purity hydrogen is introduced at 11 per minute from the gas introduction pipe 12 to replace the atmosphere in the reaction pipe 11. Next, the gas exhaust port 13 was connected to a rotary pump to reduce the pressure in the reaction tube 11 to 20-30.
Set in the range of 0 torr.

Next, after lowering the substrate temperature to 450 to 900 ° C., the H ₂ gas is changed to NH ₃ gas, N ₂ H ₄ gas or an organic compound containing N, for example, (CH ₃ ) ₂ N ₂ H ₂ , and Organic Ga compounds such as Ga (CH
₃ ) ₃ or Ga (C ₂ H ₅ ) ₃ is introduced to grow. At the same time, an organic Al compound such as Al (CH ₃ ) ₃ or Al (C ₂ H ₅ ) ₃ , an organic In compound such as I
Al (In) is added by introducing n (CH ₃ ) ₃ or In (C ₂ H ₅ ) ₃ .

When doping is performed, a doping raw material is also introduced at the same time. As a doping raw material, Si hydride such as SiH ₄ or organic Si for n type is used.
Compounds such as Si (CH ₃ ) ₄ and organic M for p-type
g compound such as (C ₅ H ₅ ) ₂ Mg, (C ₆ H ₇ ) ₂
Mg or organic Zn compound such as Zn (CH ₃ ) ₂
And so on.

Specifically, in the manufacture of the semiconductor laser shown in FIG. 9, NH ₃ is used as a raw material at 1 × 10 ^-3 mol / mi.
n, Ga (CH ₃ ) ₃ at 1 × 10 ⁻⁵ mol / min, A
1 (CH ₃ ) ₃ at 1 × 10 ⁻⁶ mol / min, In (C
H ₃ ) ₃ is introduced at 1 × 10 ⁻⁶ mol / min for growth. The substrate temperature was 1000 ° C., the pressure was 76 torr, and the total flow rate of the source gas was 1 l / min. As the dopant, Si was used as the n-type dopant and Mg was used as the p-type dopant. As a raw material for the dopant, Si (CH ₃ ) ₄ ,
Cp ₂ Mg was used.

In order to suppress the uptake of hydrogen during cooling, cooling was performed in ammonia up to a temperature of 800 ° C. to 850 ° C., and then in argon.

FIG. 10 is a schematic diagram of a semiconductor laser according to another embodiment of the present invention. 3C with (111) plane
-GaN buffer layer (undoped) on the SiC substrate 61
62 is formed to a thickness of 1 μm, and n-GaAl is formed thereon.
InN cladding layer 63 (undoped or S
i-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 ×
10 ¹⁷ cm ⁻³ ) with a thickness of 1 μm, and an active layer 64 made of undoped GaAlInN having a thickness of 0.1 μm is formed thereon.
A cladding layer 65 (Mg-doped, 1 × 10 ¹⁶ to 1 × 1) formed to a thickness of m and made of p-GaAlInN.
0 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ) is formed with a thickness of 1 μm. In the figure, reference numerals 66 and 67 denote metal electrodes.

In the semiconductor laser according to this embodiment, 3C is used.
-Since the p-type and n-type GaAlInN layers, which are the cladding layers, are formed on the SiC substrate via the GaN buffer layer to have a thickness of 1 μm, it is possible to efficiently inject current into the light emitting layer and improve the light emitting efficiency. Can be planned.

FIG. 11 is a schematic block diagram of a semiconductor laser according to another embodiment of the present invention. A GaN buffer layer (undoped) 72 having a thickness of 1 μm is formed on a 3C-SiC substrate 71 having a (111) plane, and a p-G layer is formed thereon.
The clad layer 73 made of aAlInN (Mg-doped, 1
× 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ c
m ^-3 ) is formed to a thickness of 1 μm, a light emitting layer 74 made of undoped GaAlInN is formed thereon to a thickness of 0.1 μm, and a clad layer 75 made of n-GaAlInN (undoped or Si) is further formed thereon. Dope, 1x
10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example 1 × 10 ¹⁷ cm ⁻³ )
Are formed with a thickness of 1 μm. Reference numeral 76 in the drawing,
Reference numeral 77 indicates a metal electrode.

In this semiconductor laser, the final GaAlI
Since the nN layer is an n-type, hydrogen can be prevented from being taken into the p-GaAlInN layer, and the p-type has a low resistance.
It is possible to form a GaAlInN layer. As a result, a high-luminance short-wavelength semiconductor laser can be realized.

Further, since the p-type and n-type GaAlInN layers, which are the cladding layers, can be formed with a thickness of 1 μm through the GaN buffer layer, it becomes possible to efficiently inject current into the light emitting layer, The luminous efficiency can be improved.

FIG. 12 is a schematic block diagram of a semiconductor laser according to another embodiment of the present invention. On the 3C-SiC substrate 81 having the Si surface of the (111) plane, n-Ga having a thickness of 1 μm
AlInN buffer layer 82, 1.5 μm thick n-G
a cladding layer 83 made of aAlInN, a light emitting layer 84 made of undoped GaAlInN with a thickness of 0.1 μm,
A clad layer 85 made of p-GaAlInN having a thickness of 1.5 μm is formed, and a current blocking layer 86 made of n-GaAlInN and a contact layer 87 made of p-GaAlInN are formed thereon. In the figure, reference numeral 88,
Reference numeral 89 indicates a metal electrode.

In the semiconductor laser according to this example, 3C
Since the n-GaAlInN buffer layer is formed on the (111) surface of the -SiC substrate, high-quality GaAl with low dislocations is formed.
An InN buffer layer can be grown. In addition, the p-type and n-type GaAlInN layers, which are the cladding layers, are 1.5
Since it is formed to have a thickness of μm, current can be efficiently injected into the light emitting layer, and the light emitting efficiency can be improved. When the actually obtained wafer was evaluated by X-ray diffraction, it was confirmed that crystal defects were drastically reduced, and it was found that realization of a high-luminance short-wavelength light emitting device can be expected.

FIG. 13 is a schematic configuration diagram of a semiconductor laser according to another embodiment of the present invention. In this example, in order to make the polarities of the epitaxial growth layers uniform, a 6H—SiC substrate having a Si surface on the growth surface was used. 6H-SiC substrate 9
1, a GaN buffer layer (undoped) 92 having a thickness of 1 μm is formed, and n-Ga having a thickness of 1 μm is formed thereon.
A clad layer 93 (Si-doped) made of AlInN is formed, and undoped GaA having a thickness of 0.1 μm is formed thereon.
A light emitting layer 94 made of lInN is formed, and a cladding layer 95 (Mg-doped) made of p-GaAlInN having a thickness of 1 μm is further formed thereon. In the figure, reference numeral 96 is a current blocking layer made of n-GaAlInN, 9
Reference numerals 7 and 98 denote metal electrodes, respectively.

In this semiconductor laser, the p-clad layer 9 is used.
5, an n-current blocking layer 96 is formed to prevent hydrogen from being taken into the p-clad layer 95.

FIG. 14 is a schematic configuration diagram of a semiconductor laser according to another embodiment of the present invention. 6H-Si with Si surface
GaN buffer layer (undoped) 10 on C substrate 101
2 is formed to have a thickness of 1 μm, and n-GaAlI is formed on it.
The cladding layer 103 made of nN (undoped or S
i-doped, 1 × 10 ¹⁶ to 1 × 10 ¹⁹ cm ^−3, for example, 1 ×
10 ¹⁷ cm ⁻³ ) is formed in a thickness of 1 μm, and the light emitting layer 104 made of undoped GaAlInN is formed on the 0.1
The cladding layer 105 (Mg-doped, 1 × 10 ¹⁶ to 1) formed to a thickness of μm and made of p-GaAlInN thereon.
× 10 ¹⁹ cm ^−3, for example, 1 × 10 ¹⁷ cm ⁻³ ) is formed with a thickness of 1 μm. In the figure, reference numerals 106 and 107
Indicates a metal electrode.

In the semiconductor laser according to this embodiment, since the p-type and n-type GaAlInN layers which are the cladding layers are formed to have a thickness of 1 μm, it is possible to efficiently inject a current into the light emitting layer, and the light emitting efficiency is improved. Can be improved.

In the above embodiment, the polarity of the epitaxial layer is controlled using the 6H-SiC substrate.
Another substrate such as a sapphire substrate may be used, an example of which is shown in FIGS. In each of these examples, the polarity of the crystal was confirmed by RBS.

FIG. 15 is a schematic configuration diagram of a semiconductor laser according to an example using a sapphire substrate. An AlN buffer layer 112 is formed on a sapphire substrate 111 at a growth temperature of 650 ° C., and a contact layer 113 made of p-GaAlInN, a cladding layer 114 made of p-InGaAlInN, and a light emitting layer 11 made of GaAlInN are formed on the AlN buffer layer 112.
5, the clad layer 116 made of n-GaAlInN is sequentially formed to form a semiconductor laser. In the figure,
Reference numeral 117 is a current blocking layer made of SiO ₂ , 11
Reference numerals 8 and 119 denote metal electrodes, respectively.

In this semiconductor laser, the p-clad layer 1
An n-cladding layer 116 is formed above 14 to prevent hydrogen from being taken into the p-cladding layer 114.

FIG. 16 is a schematic configuration diagram of a semiconductor laser according to another embodiment using a sapphire substrate. On the sapphire substrate 121, the AlN buffer layer 122 is 650 ° C.
Formed at the growth temperature of p-InGaAlN, the contact layer 123 made of p-InGaAlN, the cladding layer 124 made of p-InGaAlN, and the light-emitting layer 1 made of InGaAlN.
25, a cladding layer 126 made of n-InGaAlN is sequentially formed, and a semiconductor laser is formed. In the figure, reference numerals 127 and 128 respectively denote metal electrodes.

In this semiconductor laser, p-InGaAl is used.
An n-InGaAlN 126 layer is formed above the N layer 124 to prevent hydrogen from being taken into the p-InGaAlN layer 124.

FIG. 17 is a schematic configuration diagram of a semiconductor laser according to still another embodiment using a sapphire substrate. An n-GaAlInN buffer layer 132 is formed on a sapphire substrate 131, and a cladding layer 133 made of n-GaAlInN, a light emitting layer 134 made of undope GaAlInN, and a cladding layer 135 made of p-GaAlInN are sequentially formed on the n-GaAlInN buffer layer 132. A current element layer 136 made of n-GaAlInN and a contact layer 137 made of p-GaAlInN are formed thereon, thereby forming a semiconductor laser. In the figure, reference numerals 138 and 139 respectively denote metal electrodes.

This semiconductor laser was manufactured using the apparatus shown in FIG. 5 in the same manner as the embodiment shown in FIG. When the obtained semiconductor laser was evaluated by X-ray diffraction, it was confirmed that crystal defects were drastically reduced, and it was found that a high-luminance short-wavelength light emitting device can be expected to be realized.

FIG. 18 is a schematic configuration diagram of a semiconductor laser according to another embodiment of the present invention. A p-GaAlInN buffer layer 152 is formed on the p-SiC substrate 151,
A p-GaAlInN cladding layer 153 is formed thereon, an undoped GaAlInN light emitting layer 154 is formed thereon, and an n-GaAl layer having a thickness of 1 μm is further formed thereon.
The InN clad layer 155 is formed. In the figure, reference numeral 156 is a current blocking layer made of SiO ₂ , 157,
Reference numerals 158 denote metal electrodes, respectively.

In this semiconductor laser, p-S is used as the substrate.
Since the p-type electrode is connected via the p-type conductive substrate using the iC substrate, the contact resistance and the series resistance can be greatly reduced, and a high-luminance short-wavelength light emitting device can be expected to be realized. .

[0085]

As described above, according to the present invention,
By growing the GaAlInN layer on the (111) plane of the cubic SiC substrate, dislocations and strains generated due to the difference in the thermal expansion coefficient between the substrate and the growth layer are drastically reduced, and the GaAlInN layer with a low defect is formed. Growth becomes possible, high performance of the semiconductor element can be achieved, and, for example, a high-luminance short-wavelength light emitting element can be realized.

Further, since the polarity of the layer formed on the substrate is controlled and the B-plane mainly composed of the V-type element, that is, the N-plane is selectively crystal-grown so as to face the substrate, dislocation and Strain is dramatically reduced, and low defect Ga _x Al _y In
_1-xy N crystal can be grown. As a result, for example,
Since it is possible to grow a clad layer thick enough to confine carriers, it is possible to improve the performance of a semiconductor device having a pn junction and to realize a high-luminance short-wavelength semiconductor light-emitting device. .

Further, by growing and capping the n-type layer after growing the p-type layer, the p-type layer is prevented from being exposed to hydrogen during the cooling process to suppress the incorporation of hydrogen into the p-type layer. , The activation rate of the p-type dopant can be increased, and a low-resistance p-type layer can be formed. Moreover, by using the p-type conductive substrate as the substrate, the contact resistance and the series resistance can be greatly reduced, and thereby a high brightness short wavelength semiconductor light emitting device can be realized.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing changes in lattice constant of GaN and 3C—SiC with temperature.

FIG. 2 is a schematic diagram showing a Si surface and a C surface of a SiC substrate surface, respectively.

FIG. 3 is a schematic view showing GaN layers having different plane orientations which are crystal-grown on a sapphire substrate.

FIG. 4 is a sectional view showing the outline of a semiconductor laser according to an embodiment of the present invention.

5 is a diagram schematically showing the configuration of a growth apparatus used to manufacture the semiconductor laser shown in FIG.

FIG. 6 is a sectional view schematically showing the structure of an LED according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a state where an LED chip is embedded in a resin case.

FIG. 8 is a sectional view schematically showing a configuration of a semiconductor laser according to another embodiment of the present invention.

FIG. 9 is a sectional view schematically showing the structure of a semiconductor laser according to still another embodiment of the present invention.

FIG. 10 is a sectional view schematically showing the structure of a semiconductor laser according to another embodiment of the present invention.

FIG. 11 is a sectional view schematically showing the structure of a semiconductor laser according to another embodiment of the present invention.

FIG. 12 is a sectional view schematically showing the structure of a semiconductor laser according to another embodiment of the present invention.

FIG. 13 is a sectional view schematically showing the structure of a semiconductor laser according to another embodiment of the present invention.

FIG. 14 is a sectional view schematically showing the structure of a semiconductor laser according to another embodiment of the present invention.

FIG. 15 is a sectional view schematically showing the structure of a semiconductor laser according to another embodiment of the present invention.

FIG. 16 is a sectional view schematically showing the structure of a semiconductor laser according to another embodiment of the present invention.

FIG. 17 is a sectional view schematically showing the structure of a semiconductor laser according to another embodiment of the present invention.

FIG. 18 is a sectional view schematically showing the structure of a semiconductor laser according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 3C-SiC substrate 2 ... GaN buffer layer 3 ... Clad layer 4 ... Light emitting layer 5 ... Clad layer 6 ... Current blocking layer 7,8 ... Metal electrode

Claims (10)

[Claims] 1. A cubic SiC substrate and the cubic SiC substrate
Ga _x Al _y In formed on the (111) plane of the substrate
_{A 1-xy} N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) layer is provided. 2. The conductivity type of the Ga _x Al _y In _1-xy N layer is p-type, and the n-type Ga _x Al _y In _1-xy is formed on the Ga _x Al _y In _1-xy N layer. The compound semiconductor device according to claim 1, wherein an N layer is formed. 3. The conductivity type of the _{Ga x Al y In 1-xy} N layer is p-type, on top of the _{Al x Ga 1-xy In y} N layer, _{Ga x Al y In 1-xy} N layer And n-type Ga _x Al _y
The compound semiconductor device according to claim 1, wherein In _1-xy N layers are sequentially formed. 4. A substrate and Ga _x formed on the substrate
An Al _y In _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) layer, and the crystal plane of the Ga _x Al _y In _1-xy N layer facing the substrate is an N-plane. The compound semiconductor element which has a pn junction characterized by these. 5. The compound semiconductor device according to claim 4, wherein the substrate is made of SiC. 6. The Ga _x Al _y In of the substrate
The compound semiconductor device according to claim 5, wherein the surface on which the _1-xy N layer is formed is a Si surface. 7. The compound semiconductor device according to claim 4, wherein the substrate is made of sapphire, and a buffer layer made of single-crystal Ga _x Al _y In _1-xy N is formed on the substrate. . 8. A p-type conductive substrate, and a p-type Ga _x Al _y In _1-xy N (0 ≦ x) formed on the p-type conductive substrate.
≦ 1,0 ≦ y ≦ 1) layer and this p-type Ga _x Al _y In
_{1-xy N (0 ≦ x} ≦ 1,0 ≦ y ≦ 1) n -type formed on layer _{Ga x Al y In 1-xy} N (0 ≦ x ≦ 1,0 ≦ y ≦
1) A compound semiconductor device comprising a layer. 9. The compound semiconductor device according to claim 8, wherein the p-type conductive substrate is made of p-type SiC. 10. The p-type Ga _{x of the} p-type conductive substrate
On the surface opposite to the Al _y In _1-xy N layer and on the n-type Ga _x
The compound semiconductor device according to claim 8, wherein a pair of electrodes is formed on the Al _y In _1-xy N layer.