JP3456980B2 - Method for forming compound semiconductor layer - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention can be applied to the manufacture of semiconductor lasers and light emitting diodes capable of emitting light in the blue region.
And a method for forming a compound semiconductor layer .

[0002]

2. Description of the Related Art Conventionally, the group V element is nitrogen (N) III
Since the group V compound semiconductor has a wide energy gap, it has attracted attention as a light emitting material in the visible and ultraviolet regions.
Among them, light emitting elements such as a semiconductor laser and a light emitting diode capable of emitting light in the blue region have been studied using an AlGaN-based material.

FIG. 3 is a schematic sectional view of a conventional AlGaN semiconductor laser [or light emitting diode]. In addition,
The value in [] is for a light emitting diode.

This element is formed on a sapphire substrate 101.
A thin buffer layer 102 made of GaN or AlN is formed, on which an n-type GaN layer 103 and an n-type AlG are formed.
aN lower clad layer 104, undoped AlGaInN
System active layer [Zn-doped AlGaInN system light emitting layer]
105, p-type AlGaN upper cladding layer 107, p-type G
The aN cap layer 108 is laminated.

A p-type electrode 90 is formed on the p-type GaN cap layer 108. In addition, the n-type GaN layer 103
Of the upper n-type lower clad layer 104, the active layer [or the light emitting layer] 105, the p-type upper clad layer 107 and the p-type cap layer 108 are partially removed and exposed. The n-type electrode 100 is formed on the portion of the n-type GaN layer 103.

This semiconductor laser [or light emitting diode] is manufactured as follows.

First, metalorganic vapor phase epitaxy (MOCVD
Surface treatment of the sapphire substrate 101 at about 1050 ° C., and then the substrate temperature is lowered to about 500 ° C. to grow a thin buffer layer 102 made of GaN or AlN.

Next, the substrate temperature is raised to about 1020 ° C. and n
-Type GaN layer 103 is formed, and then n-type AlGaN is formed.
The lower clad layer 104 is grown to about 1 μm.

Subsequently, the substrate temperature is lowered to about 800 ° C. and the non-doped AlGaInN active layer [or Zn-doped light emitting layer] 105 is grown to about 100 Å to 500 Å.

Thereafter, the substrate temperature is raised to about 1020 ° C. to grow the p-type AlGaN upper clad layer 107 to about 1 μm, and then the p-type GaN cap layer 108 is grown.

[0011]

In the above conventional semiconductor laser [or light emitting diode], in order to effectively confine light in the active layer and the cladding layer and effectively inject the injection current in the active layer, the upper cladding layer 107 is used. The layer thickness of the lower clad layer 104 needs to be about 1 μm.

However, in the conventional semiconductor laser [or light emitting diode] device structure and manufacturing method, as shown in FIGS. 4 and 5, the AlGaN lower cladding layer 104 is formed.
Of about 1 μm, cracks 109
Occurred, and it was difficult to obtain a good quality clad layer.

An object of the present invention is to form a compound semiconductor layer capable of avoiding the occurrence of such a crack, and more specifically, it is an Al _y Ga _1-y N 2 film formed on a substrate by MOCVD.
(0 <y <1) lower cladding layer and upper cladding layer
It is intended to solve the problem of the occurrence of cracks on the surface when forming a compound semiconductor layer as a pad layer .

[0014]

A method of forming a compound semiconductor layer according to the present invention is a method of forming Al on a substrate by MOCVD.
_In the method of forming a compound semiconductor layer made of _y Ga _1-y N (0 <y <1), the compound semiconductor layer is formed on the substrate.
From the side, the lower clad layer and the active layer or the light emitting layer
And at least an upper clad layer
In the lower clad layer and the upper clad layer of the light emitting device,
It is characterized by forming a single buffer layer or a plurality of buffer layers in the lower clad layer and the upper clad layer.

[0015]

Al _y Ga _1-y N with a buffer layer in it
A GaN layer may be provided between the (0 <y <1) layer and the substrate.

[0017]

The operation of the present invention will be described below.

In the present invention, the lower clad layer and
By repeating the growth of the buffer layer in the upper clad layer once or a plurality of times, it is possible to grow the lower clad layer and the upper clad layer having a good surface morphology and no cracks to a desired thickness.

For example, by repeatedly growing an Al _y Ga _1-y N (0 <y <1) cladding layer and an Al _x Ga _1-x N (0 ≦ x ≦ 1) buffer layer, the lower cladding layer and the The thickness of the upper clad layer can be about 1 μm.

[0021] Thus using the upper cladding layer and lower cladding layer of a thick film of good _{quality, Al w Ga z In 1-} wz N
(The AlGaInN semiconductor laser device and the light emitting diode can be realized by using 0 ≦ w ≦ 1 and 0 ≦ z ≦ 1 as the active layer or the light emitting layer.

The buffer layer made of GaN is made of Al _y Ga _1-y N
(0 <y <1) The growth temperature may be higher than the growth temperature of the cladding layer, but Al _y Ga _1-y N (0 <y <
1) When grown at a growth temperature lower than the growth temperature of the cladding layer, there is no effect of evaporation of the buffer layer, and a better layer can be obtained.

AlN or Al _x Ga _1-x N (0 <x <
The buffer layer composed of 1) is Al _y Ga _1-y N (0 <y <1).
The growth temperature may be lower than the growth temperature of the clad layer, but since it is not necessary to consider evaporation of the buffer layer, Al
It can be grown at a growth temperature equal to or higher than the growth temperature of the _y Ga _1-y N (0 <y <1) cladding layer, and is easy to manufacture.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In addition, in the following figures,
Portions having the same function are indicated by the same numbers.

(Embodiment 1) FIG. 1 is a sectional view showing an AlGaN / InGaN / AlGaN semiconductor laser [or a light emitting diode] according to an embodiment of the present invention.

In this device, a thin buffer layer 2 made of GaN or AlN is formed on a sapphire substrate 1, and an n-type GaN layer 3, an n-type lower clad layer 4 and a non-doped or Si-doped Al layer are formed on the buffer layer 2. _w Ga _z In _1-wz
N (0 ≦ w ≦ 1, 0 ≦ z ≦ 1) active layer [or light emitting layer]
6, a p-type upper clad layer 7 and a p-type GaN cap layer 9 are laminated.

The n-type lower clad layer 4 contains n-type Al _y.
The Ga _1-y N (0 <y <1) clad layers 4 a and the thin n-type Al _x Ga _1-x N (0 ≦ x ≦ 1) buffer layers 5 are alternately laminated to form the lower clad layer 4. Has a thickness of about 1 μm. In the p-type upper clad layer 7, p-type A
l _y Ga _1-y N (0 <y <1) clad layer 7a and thin layer p
Type Al _x Ga _1-x N (0 ≦ x ≦ 1) buffer layers 8 are alternately laminated to form a thickness of the upper clad layer 7 of about 1 μm.

A p-type electrode 10 is formed on the p-type cap layer 9. Further, the n-type lower clad layer 4, the active layer [or the light emitting layer] 6, the p-type upper clad layer 7, the p-type buffer layer 8 and the p-type buffer layer 8 and the p-type buffer layer 8 and the p-type buffer layer 8 and the p-type buffer layer 8 and the p-type buffer layer 8 and the p-type buffer layer 8 are provided so that the upper portion of the n-type GaN layer 3 is partially exposed. The mold cap layer 9 is partially removed, and the n-type electrode 11 is formed on the exposed part of the n-type GaN layer 3.

In the first embodiment, the thickness is about 0.15.
0.3 μm n-type Al_0.1Ga_0.9N-clad layer 4a and thickness
The n-type GaN buffer layer 5 having a thickness of about 200 Å
It is repeatedly grown to about 1 μm. Also, the thickness is about
0.15-0.3 μm p-type Al _0.1Ga_0.9N-clad
Layer 7a and p-type GaN with a thickness of about 200 Å
The barrier layer 8 and the lower cladding layer 4 and the upper cladding layer 4 are grown repeatedly.
The partial cladding layer 7 has a thickness of about 1 μm. Also, live
The thickness of the light-transmitting layer [or the light-emitting layer] 6 is about 200 Å.
Stromm undoped or Si-doped Ga_0.2In
_0.8The N layer is formed.

This semiconductor laser [or light emitting diode] is manufactured as follows.

The growth of each semiconductor layer is carried out by the MOCVD method, and a sapphire (0001) C plane is used as a substrate.
Trimethylgallium (TMG) as a group III gas source,
Trimethyl aluminum (TMA) and trimethyl indium (TMI) are used, and ammonia (NH ₃ ) is used as a group V gas source. Monosilane (SiH ₄ ) is used as the n-type dopant source, and biscyclopentadienyl magnesium (Cp ₂ Mg) is used as the p-type dopant source.
To use. Further, H ₂ is used as the carrier gas.

First, the sapphire substrate 1 is introduced into the MOCVD apparatus, and the substrate is surface-treated by heating the substrate in H ₂ at a substrate temperature of about 1050 ° C. Next, the substrate temperature is lowered to about 500 ° C. and the buffer layer 2 made of GaN or AlN is grown. The thickness of the buffer layer made of GaN is 250 angstroms, and the thickness of the buffer layer made of AlN is 500 angstroms.

Next, the substrate temperature is raised to about 1020 ° C. and n
The type GaN layer 3 is grown to a thickness of about 4 μm.

Then, at the same substrate temperature, n-type Al _0.1 Ga
_{The 0.9} N clad layer 4a is grown to about 0.15 μm to 0.3 μm, and then the substrate temperature is lowered to about 500 ° C. to n-type G
The aN buffer layer 5 is grown to about 200 Å.
Further, the growth of the n-type cladding layer 4a / n-type buffer layer 5 is repeated to make the thickness of the lower cladding layer 4 about 1 μm.

Next, non-doped or Si-doped In _0.2 Ga _{0 .8} N active layer and the substrate temperature to about 800 ° C. [or light emitting layer] 6 is grown thickness of about 200 angstroms.

Subsequently, the substrate temperature is raised to about 1020 ° C. and the p-type Al _0.1 Ga _0.9 N cladding layer 7a is set to about 0.15 μm.
~ 0.3μm growth, then substrate temperature about 500 ℃
And the p-type GaN buffer layer 8 is grown to about 200 Å. Further, the growth of the p-type cladding layer 7a / p-type buffer layer 8 is repeated to make the thickness of the upper cladding layer 7 about 1 μm.

Subsequently, the p-type GaN cap layer 9 is grown to a thickness of about 1 μm.

About 700 ° C. for the wafer after growth, N
_The p-type buffer layer 8, the p-type cladding layer 7a, and the p-type cap layer 9 are changed into a high-concentration p-type layer by performing thermal annealing in ₂ atmospheres.

After that, n-type G is formed to form the n-type electrode 11.
Etching is performed until the aN layer 3 is exposed, and an n-type current 11 is formed on the n-type GaN layer 3 exposed by the etching.
A p-type current 10 is formed on the p-type cap layer 9.

The growth of the GaN buffer layer is about 1000.
The growth temperature may be the same as or higher than that of the clad layer, such as C. or about 1200.degree. C., but considering the evaporation of the GaN buffer layer, the growth temperature is preferably about 500.degree. C. lower than that of the clad layer. .

In the first embodiment, since the GaN buffer layer is formed between the AlGaN clad layers, the crystal growth of the good quality AlGaN clad layer having a good surface condition and no cracks was possible. Since a high-quality thick clad layer can be obtained in this manner, it is possible to realize an AlGaInN-based semiconductor laser and a light emitting diode which are excellent in mass productivity and have good electric and optical characteristics.

(Embodiment 2) In Embodiment 2, an n-type Al _0.3 Ga _0.7 N cladding layer 4a having a thickness of about 0.15 to _0.3 μm and an n-type GaN having a thickness of about 200 Å are used.
The p-type A having a thickness of about 0.15 to 0.3 μm is formed by repeatedly growing the buffer layer 5 to make the thickness of the lower clad layer 4 about 1 μm.
The _0.3 Ga _0.7 N cladding layer 7a and the p-type GaN buffer layer 8 having a thickness of about 200 Å are repeatedly grown to make the thickness of the upper cladding layer 7 about 1 μm. As the active layer [or the light emitting layer] 6, a non-doped or Si-doped Ga _0.2 In _0.8 N layer having a thickness of about 200 Å is formed as in the first embodiment. Other structures are similar to those of the first embodiment.

This semiconductor laser [or light emitting diode] is manufactured as follows.

The growth of each semiconductor layer is the same as in the first embodiment.
Performed by OCVD method, and sapphire (000
1) Use the C plane. As the group III gas source, the group V gas source, the n-type dopant source, the p-type dopant source, and the carrier gas, those similar to those in the first embodiment are used.

First, similarly to the first embodiment, the buffer layer 2 and the n-type GaN layer 3 are grown on the sapphire substrate 1.

Then, about 1020 which is the same as that of the n-type GaN layer 3 is formed.
The n-type Al _0.3 Ga _0.7 N cladding layer 4a is grown at about 0.15 μm to _0.3 μm at the substrate temperature of ° C, and then the substrate temperature is lowered to about 500 ° C to form the n-type GaN buffer layer 5 at about 200 ° C.
Grow angstroms. Further, the growth of the n-type cladding layer 4a / n-type buffer layer 5 is repeated to make the thickness of the lower cladding layer 4 about 1 μm.

Next, the active layer [or the light emitting layer] 6 is grown in the same manner as in the first embodiment.

Subsequently, the substrate temperature is raised to about 1020 ° C. and the p-type Al _0.3 Ga _0.7 N cladding layer 7a is set to about 0.15 μm.
~ 0.3μm growth, then substrate temperature about 500 ℃
And the p-type GaN buffer layer 8 is grown to about 200 Å. Further, the growth of the p-type cladding layer 7a / p-type buffer layer 8 is repeated to make the thickness of the upper cladding layer 7 about 1 μm.

Subsequently, the p-type cap layer 9 is grown in the same manner as in the first embodiment, and the p-type buffer layer 8, the p-type cladding layer 7a and the p-type cap layer 9 are changed to the high-concentration p-type layer. Then, the p-type electrode 10 and the n-type electrode 11 are formed in the same manner as in the first embodiment.

The growth of the GaN buffer layer is about 1000.
The growth temperature may be the same as or higher than that of the clad layer, such as C. or about 1200.degree. C., but considering the evaporation of the GaN buffer layer, the growth temperature is preferably about 500.degree. C. lower than that of the clad layer. .

Also in the second embodiment, since the GaN buffer layer is formed between the AlGaN clad layers, the crystal growth of the good quality AlGaN clad layer having a good surface condition and no cracks was possible. Since a high-quality thick clad layer can be obtained in this manner, it is possible to realize an AlGaInN-based semiconductor laser and a light emitting diode which are excellent in mass productivity and have good electric and optical characteristics.

(Embodiment 3) In this Embodiment 3, an n-type Al _0.1 Ga _0.9 N cladding layer 4 a having a thickness of about 0.15 to 0.3 μm and an n-type AlN having a thickness of about 200 Å are used.
The p-type A having a thickness of about 0.15 to 0.3 μm is formed by repeatedly growing the buffer layer 5 to make the thickness of the lower clad layer 4 about 1 μm.
The thickness of the upper clad layer 7 is set to about 1 μm by repeatedly growing the _0.1 Ga _0.9 N clad layer 7a and the p-type AlN buffer layer 8 having a thickness of about 200 Å. As the active layer [or the light emitting layer] 6, a non-doped or Si-doped Ga _0.2 In _0.8 N layer having a thickness of about 200 Å is formed as in the first embodiment. Other structures are similar to those of the first embodiment.

This semiconductor laser [or light emitting diode] is manufactured as follows.

The growth of each semiconductor layer is the same as in the first embodiment.
Performed by OCVD method, and sapphire (000
1) Use the C plane. As the group III gas source, the group V gas source, the n-type dopant source, the p-type dopant source, and the carrier gas, those similar to those in the first embodiment are used.

First, similarly to the first embodiment, the buffer layer 2 and the n-type GaN layer 3 are grown on the sapphire substrate 1.

Subsequently, about 1020 which is the same as that of the n-type GaN layer 3 is formed.
The n-type Al _0.1 Ga _0.9 N cladding layer 4a is grown at about 0.15 μm to 0.3 μm at a substrate temperature of ° C., and then the substrate temperature is set at about 1000 ° C. or about 1200 ° C.
The buffer layer 5 is grown to about 200 Å. Further, the growth of the n-type cladding layer 4a / n-type buffer layer 5 is repeated to make the thickness of the lower cladding layer 4 about 1 μm.

Next, the active layer [or the light emitting layer] 6 is grown in the same manner as in the first embodiment.

Subsequently, the substrate temperature is raised to about 1020 ° C. and the p-type Al _0.1 Ga _0.9 N cladding layer 7a is set to about 0.15 μm.
~ 0.3μm growth, then substrate temperature about 500 ℃
And the p-type AlN buffer layer 8 is grown to about 200 angstroms. Further, the growth of the p-type cladding layer 7a / p-type buffer layer 8 is repeated to make the thickness of the upper cladding layer 7 about 1 μm.

Subsequently, the p-type cap layer 9 is grown in the same manner as in the first embodiment, and the p-type buffer layer 8, the p-type upper clad layer 7 and the p-type cap layer 9 are changed to a high-concentration p-type layer. .

After that, the p-type electrode 10 and the n-type electrode 11 are formed in the same manner as in the first embodiment.

The growth temperature of the AlN buffer layer is about 50.
Although the temperature may be as low as 0 ° C., the evaporation of the AlN buffer layer need not be taken into consideration, and a high temperature such as about 1000 ° C. or about 1200 ° C. is preferable. Further, since the growth can be performed without lowering the temperature during the growth, the manufacturing becomes easy.

In the third embodiment, since the AlN buffer layer is formed between the AlGaN cladding layers, the crystal growth of the AlGaN cladding layer having a good surface condition and no cracks was possible. Since a high-quality thick clad layer can be obtained in this manner, it is possible to realize an AlGaInN-based semiconductor laser and a light emitting diode which are excellent in mass productivity and have good electric and optical characteristics.

(Embodiment 4) In this Embodiment 4, an n-type Al _0.3 Ga _0.7 N cladding layer 4 a having a thickness of about 0.15 to _0.3 μm and an n-type Al having a thickness of about 200 Å are used.
_0.05 Ga _0.95 N buffer layer 5 was repeatedly grown to make the thickness of the lower cladding layer 4 about 1 μm, and the thickness was about 0.15 to 0.
A p-type Al _0.3 Ga _0.7 N clad layer 7a having a thickness of 3 μm and a p-type Al _0.05 Ga _0.95 N buffer layer 8 having a thickness of approximately 200 Å are repeatedly grown to make the thickness of the upper clad layer 7a approximately 1 μm. In addition, the active layer [or the light emitting layer] 6
As in the first embodiment, a non-doped or Si-doped Ga _0.2 In _0.8 film having a thickness of about 200 Å is used.
The N layer is formed. Other structures are similar to those of the first embodiment.

This semiconductor laser [or light emitting diode] is manufactured as follows.

The growth of each semiconductor layer is M as in the first embodiment.
Performed by OCVD method, and sapphire (000
1) Use the C plane. As the group III gas source, the group V gas source, the n-type dopant source, the p-type dopant source, and the carrier gas, those similar to those in the first embodiment are used.

First, similarly to the first embodiment, the buffer layer 2 and the n-type GaN layer 3 are grown on the sapphire substrate 1.

Subsequently, about 1020, which is the same as that of the n-type GaN layer 3, is formed.
The n-type Al _0.3 Ga _0.7 N cladding layer 4a is grown at about 0.15 μm to _0.3 μm at a substrate temperature of ° C., and then the substrate temperature is set at about 1000 ° C. or about 1200 ° C.
_{A 0.05} Ga _0.95 N buffer layer 5 is grown to about 200 Å. Further, the growth of the n-type cladding layer 4a / n-type buffer layer 5 is repeated to make the thickness of the lower cladding layer 4 about 1 μm.

Next, the active layer [or the light emitting layer] 6 is grown in the same manner as in the first embodiment.

Subsequently, the substrate temperature is raised to about 1020 ° C. and the p-type Al _0.3 Ga _0.7 N cladding layer 7a is set to about 0.15 μm.
~ 0.3 μm, and then the substrate temperature is about 1000
The p-type Al _0.05 Ga _0.95 N buffer layer 8 is grown at about 200 Å at about 200 Å. Further, the growth of the p-type cladding layer 7a / p-type buffer layer 8 is repeated to make the thickness of the upper cladding layer 7 about 1 μm.

Subsequently, the p-type cap layer 9 is grown in the same manner as in the first embodiment, and the p-type buffer layer 8, the p-type cladding layer 7a and the p-type cap layer 9 are changed to the high-concentration p-type layer. Then, the p-type electrode 10 and the n-type electrode 11 are formed in the same manner as in the first embodiment.

The growth temperature of the AlN buffer layer is about 50.
Although the temperature may be as low as 0 ° C., the evaporation of the AlN buffer layer need not be taken into consideration, and a high temperature such as about 1000 ° C. or about 1200 ° C. is preferable. Further, since the growth can be performed without lowering the temperature during the growth, the manufacturing becomes easy.

In the fourth embodiment, since the AlGaN buffer layer is formed between the AlGaN cladding layers, the surface condition is good and the AlGaN is of good quality without cracks.
Crystal growth of the clad layer was possible. Since a high-quality thick clad layer can be obtained in this manner, it is possible to realize an AlGaInN-based semiconductor laser and a light emitting diode which are excellent in mass productivity and have good electric and optical characteristics.

(Fifth Embodiment) FIG. 2 is a sectional view showing an AlGaN / InGaN / AlGaN semiconductor laser [or a light emitting diode] according to another embodiment of the present invention.

In this device, a thin buffer layer 2 made of GaN or AlN is formed on a sapphire substrate 1, and an n-type GaN layer 3, an n-type lower clad layer 4 and a non-doped or Si-doped Al layer are formed on the buffer layer 2. _w Ga _z In _1-wz
N (0 ≦ w ≦ 1, 0 ≦ z ≦ 1) active layer [or light emitting layer]
6, a p-type upper clad layer 7 and a p-type GaN cap layer 9 are laminated.

In the n-type lower clad layer 4, n-type Al _y
In the p-type upper clad layer 7, a Ga _1-y N (0 <y <1) clad layer 4a and a thin n-type Al _x Ga _1-x N (0 ≦ x ≦ 1) buffer layer 5 are formed. the, p-type Al _y Ga _1-y N
(0 <y <1) clad layer 7a and thin p-type Al _x Ga layer
_{The 1-x} N (0 ≦ x ≦ 1) buffer layer 8 is laminated and the thickness of the lower clad layer 4 and the upper clad layer 7 is about 1 μm.
Has been to a degree.

A p-type electrode 10 is formed on the p-type cap layer 9. The n-type lower clad layer 4, the active layer [or the light emitting layer] 6, the p-type upper clad layer 7, the p-type buffer layer 8 and the p-type cap layer 9 are formed so that the n-type GaN layer 3 is partially exposed. Partially removed, the n-type electrode 11 is formed on the exposed part of the n-type GaN 3.

In the fifth embodiment, the lower cladding layer 4
Is an n-type Al _0.1 Ga _0.9 N cladding layer 4a having a thickness of about 0.3 μm, an n-type GaN buffer layer 5 having a thickness of about 200 Å, an n-type Al _0.1 Ga _0.9 N cladding layer 4a having a thickness of about 0.25 μm, and a thickness of about 200 angstrom n-type G
aN buffer layer 5 and the thickness of about 0.15 [mu] m n-type Al _{0. 1}
The Ga _0.9 N cladding layer 4a is sequentially grown. Also,
The upper clad layer 7 is made of p-type Al having a thickness of about 0.15 μm.
_0.1 Ga _0.9 N clad layer 7a, p-type GaN buffer layer 8 with a thickness of about 200 Å, p with a thickness of about 0.25 μm
-Type Al _0.1 Ga _0.9 N cladding layer 7 a, p-type GaN buffer layer 8 having a thickness of about 200 Å, and thickness of about 0.3
A p-type Al _0.1 Ga _0.9 N cladding layer 7a having a thickness of μm is sequentially grown. Further, as the active layer [or the light emitting layer] 6, a non-doped or Si-doped Ga _0.2 In _0.8 N layer having a thickness of about 200 Å is formed as in the first embodiment. Other structures are similar to those of the first embodiment.

This semiconductor laser [or light emitting diode] is manufactured as follows.

The growth of each semiconductor layer is M as in the first embodiment.
Performed by OCVD method, and sapphire (000
1) Use the C plane. As the group III gas source, the group V gas source, the n-type dopant source, the p-type dopant source, and the carrier gas, those similar to those in the first embodiment are used.

First, similarly to the first embodiment, the buffer layer 2 and the n-type GaN layer 3 are grown on the sapphire substrate 1.

Subsequently, about 1020 which is the same as that of the n-type GaN layer 3 is used.
The n-type Al _0.3 Ga _0.7 N cladding layer 4a was grown to a thickness of about 0.3 μm at a substrate temperature of 500 ° C.
And the n-type GaN buffer layer 5 is grown to about 200 angstroms. Next, at the substrate temperature of about 1020 ° C., n-type A
The l _0.3 Ga _0.7 N cladding layer 4a is grown to about 0.25 μm, and then the substrate temperature is lowered to about 500 ° C. to form n-type GaN.
The buffer layer 5 is grown to about 200 Å. Further, the n-type Al _0.3 Ga _0.7 N cladding layer 4a is grown by about 0.15 μm at the substrate temperature of about 1020 ° C.

Next, the active layer [or the light emitting layer] 6 is grown in the same manner as in the first embodiment.

Then, the substrate temperature is raised to about 1020 ° C. and the p-type Al _0.3 Ga _0.7 N cladding layer 7a is set to about 0.15 μm.
After the growth, the substrate temperature is lowered to about 500 ° C. and the p-type GaN buffer layer 8 is grown to about 200 Å. Next, at a substrate temperature of about 1020 ° C., p-type Al _0.3 Ga
_{The 0.7} N cladding layer 7a is grown to about 0.25 μm, and then the substrate temperature is lowered to about 500 ° C. to p-type GaN buffer layer 8
Is about 200 angstroms. Furthermore, about 1
A p-type Al _0.3 Ga _0.7 N cladding layer 7a is grown to a thickness of about 0.3 μm at a substrate temperature of 020 ° C.

Subsequently, similarly to the first embodiment, the p-type cap layer 9 is grown to change the p-type buffer layer 8, the p-type cladding layer 7a and the p-type cap layer 9 into the high-concentration p-type layer. Then, the p-type electrode 10 and the n-type electrode 11 are formed in the same manner as in the first embodiment.

The growth of the GaN buffer layer is about 1000.
The growth temperature may be the same as or higher than that of the clad layer, such as C. or about 1200.degree. C., but considering the evaporation of the GaN buffer layer, the growth temperature is preferably about 500.degree. C. lower than that of the clad layer. .

In the fifth embodiment, since the GaN buffer layer is formed between the AlGaN cladding layers, the crystal growth of the AlGaN cladding layer having a good surface condition and no cracks was possible. Moreover, since the AlGaN cladding layer is made thinner as it approaches the active layer [or the light emitting layer], the crystalline state of the cladding layer can be further improved. Since a high quality and thick clad layer is obtained in this manner, it is possible to realize an AlGaInN-based semiconductor laser and a light emitting diode which are excellent in mass productivity and have good electric and optical characteristics.

The present invention is not limited to the above embodiment, and growth conditions, kinds of organometallic compound gas, materials used, etc. other than those shown in the above embodiment can be used.

[0088]

As is apparent from the above description, according to the present invention, Al _y Ga _{1-y is formed} on a substrate by MOCVD.
In the method of forming a compound semiconductor layer made of N (0 <y <1), the compound semiconductor layer is sequentially formed from the substrate side.
Next, the lower cladding layer, the active layer or the light emitting layer, and the upper cladding layer.
Of a compound semiconductor light emitting device including at least a rud layer
The lower clad layer and the upper clad layer,
By forming a single buffer layer or a plurality of buffer layers in the lower clad layer and the upper clad layer, a good quality of the clad layer and the upper clad layer with good surface condition and no cracks can be obtained.
The pad layer can be grown to a desired thickness.

In the case of an Al _y Ga _1-y N (0 <y <1) clad layer, by repeatedly growing an Al _x Ga _1-x N (0 ≦ x ≦ 1) buffer layer and a clad layer, It is possible to grow the upper clad layer and the lower clad layer to about 1 μm. The upper cladding layer, the lower cladding layer and the _{Al w Ga z In 1-wz} N (0 ≦ w ≦ 1,0 ≦ z ≦ 1)
Due to the active layer [or light emitting layer], it has excellent mass productivity and electrical characteristics.
It is possible to realize an AlGaInN-based semiconductor laser device and a light-emitting diode having good properties and optical characteristics .

[0090]

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a semiconductor laser [or a light emitting diode] according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a semiconductor laser [or a light emitting diode] according to another embodiment of the present invention.

FIG. 3 Conventional semiconductor laser [or light emitting diode]
It is a cross-sectional schematic diagram which shows.

FIG. 4 is a schematic plan view showing the surface of an AlGaN cladding layer in a conventional semiconductor laser.

FIG. 5 is a schematic sectional view showing a manufacturing process of an AlGaN cladding layer in a conventional semiconductor laser.

[Explanation of symbols]

1 Sapphire (0001) substrate 2 GaN or AlN buffer layer 3 n-type GaN layer 4 lower cladding layer 4a n-type Al _y Ga _1-y N (0 <y <1) cladding layer 5 thin layer n-type Al _x Ga _{1- x N (0 ≦ x ≦ 1} ) buffer layer 6 doped or Si-doped Al _w Ga _z In
_1-wz N (0 ≦ w ≦ 1, 0 ≦ z ≦ 1) active layer or light-emitting layer 7 upper clad layer 7a p type Al _y Ga _1-y N (0 <y <1) clad layer 8 thin layer p type Al _x Ga _1-x N (0 ≦ x ≦ 1) buffer layer 9 p-type GaN cap layer 10 p-type electrode 11 n-type electrode

Claims (4)

(57) [Claims] 1. An Al _y G film is formed on a substrate by MOCVD.
a _1-y N (0 <y <1), the compound semiconductor layer is formed on the substrate side.
Sequentially from the lower clad layer, the active layer or the light emitting layer,
Compound semiconductor light emission including at least an upper cladding layer
The lower clad layer and the upper clad layer of the device.
A method for forming a compound semiconductor layer, comprising forming a single buffer layer or a plurality of buffer layers in the lower clad layer and the upper clad layer. 2. The buffer layer comprises Al _x Ga _1-x N (0 ≦ x
The method of forming a compound semiconductor layer according to claim 1, wherein the compound semiconductor is formed of ≦ 1). 3. The lower clad layer including the buffer layer
And the compound semiconductor layer as the upper clad layer is 1 μm
3. The structure according to claim 1, which has a thickness of about m.
A method for forming a compound semiconductor layer according to any one of 1. 4. The buffer layer comprises the lower cladding layer and the buffer layer.
And Al _y Ga _1-y N (0 <y < as the upper clad layer
1) The method for forming a compound semiconductor layer according to any one of claims 1 to 3, wherein the compound semiconductor layer is formed at a temperature different from the formation temperature of the compound semiconductor layer.