JP2000077783A - Growth method of indium-containing nitride semiconductor crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a quantum well layer and a barrier layer against damage by a method wherein an In-containing first nitride semiconductor layer is formed, a substrate is made to rise in temperature as a second another nitride semiconductor layer is formed, an In-free third nitride semiconductor layer is formed, and a first to a third process are successively carried out. SOLUTION: When the semiconductor layers of a nitride laser are formed through a crystal growth method, an In-containing multi-quantum well structure active layer 107 is formed keeping a substrate at a temperature of 750 deg.C. The substrate temperature is made to rise from 750 deg.C to 1050 deg.C as a P-type GaN layer 114 is formed, and then an In-free P-type GaN optical guide layer 109 is formed at a temperature of 1050 deg.C. As mentioned above, the substrate is raised in temperature as the GaN layer 114 is formed after the In-containing active layer 107 is formed, so that In and Ga can be prevented from evaporating while the substrate is raised in temperature so as not to cause damage to a quantum well layer and a barrier layer above the active layer 107.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for growing a nitride semiconductor crystal containing indium, and more particularly to a method for stably forming a semiconductor layer containing indium by crystal growth.

[0002]

2. Description of the Related Art Gallium nitride has a higher forbidden band energy of 3.4 eV than other compound semiconductors such as indium phosphide and gallium arsenide. Therefore, a gallium nitride-based semiconductor is used, and a semiconductor having nitrogen as a constituent element, that is, a device using a nitride semiconductor (hereinafter, referred to as a nitride semiconductor device), particularly emits light at a relatively short wavelength from green to ultraviolet. Element (hereinafter, referred to as a nitride semiconductor light emitting element),
For example, light emitting diodes (hereinafter, nitride light emitting diodes) and semiconductor lasers (hereinafter, nitride semiconductor lasers) have been realized (for example, S. Nakamura et al., Jpn. J. Appl.
Phys. 35 (1996) L74).

Conventional Example 1 FIG. 4 is a cross-sectional view of a nitride semiconductor laser manufactured by a conventional method for growing a nitride semiconductor crystal containing indium (Japanese Patent Laid-Open No. 10-27939). In Conventional Example 1,
Nitride semiconductor lasers are manufactured by metal organic chemical vapor deposition (MOVPE). A buffer layer 32 made of GaN is formed on the surface of a sapphire substrate 31 having the A-plane as a main surface.
It is grown to a thickness of 00 °. Subsequently, the temperature is increased to 1050 ° C., and an n-type contact layer 33 made of Si-doped n-type GaN is grown to a thickness of 4 μm. Next, raise the temperature to 750
C., and a crack preventing layer 34 made of Si-doped In ₀ .Ga _0.9 N is grown to a thickness of 500 °.

Next, the temperature is set to 1050 ° C., and the n-type optical confinement layer 3 made of Si-doped n-type Al _0.3 Ga _0.7 N
5 is grown to a thickness of 0.5 μm. Subsequently, an n-type light guide layer 36 made of Si-doped n-type GaN is grown to a thickness of 500 °. Next, the active layer 37 is grown. The active layer is maintained at a temperature of 750 ° C.
_A well layer of _0.2 Ga _0.8 N is grown to a thickness of 25 °. Next, at the same temperature, the non-doped In _0.01 Ga _0.95
A barrier layer made of N is grown to a thickness of 50 °. This operation was repeated five times, and finally the well layer was grown to a total film thickness of 37.
An active layer 37 having a multiple quantum well structure with a thickness of 5 ° is grown.

After growing the active layer 37, the temperature is increased to 105
At 0 ° C., a p-type cap layer 38 made of Mg-doped p-type Al _0.2 Ga _0.8 N is grown to a thickness of 100 °. Next, while maintaining the temperature at 1050 ° C., a p-type optical guide layer 39 made of Mg-doped p-type GaN is grown to a thickness of 500 °. Subsequently, a p-type optical confinement layer 40 made of Mg-doped Al _0.3 Ga _0.7 N is grown to a thickness of 0.5 μm. Subsequently, a p-type contact layer 41 made of Mg-doped p-type GaN is grown to a thickness of 0.5 μm.

Next, reactive ion etching (RIE)
The apparatus etches the wafer from the uppermost p-type contact layer 41 to expose the surface of the n-type contact layer 33 where the negative electrode 43 is to be formed. Next, the p-type contact layer 41 and the p-type optical confinement layer 40 are etched from above the p-type contact layer 41 by the same RIE.
Etching is performed in a stripe shape having a width of μm to form a ridge shape. Next, a positive electrode 42 containing Ni and Au is formed on the surface of the p-type contact layer. On the other hand, a continuous striped negative electrode 43 made of Ti and Al is formed on the previously exposed n-type contact layer 33.

Conventional Example 2 FIG. 5 is a cross-sectional view of a nitride semiconductor laser manufactured by a conventional method for growing a nitride semiconductor crystal containing indium (Japanese Patent Laid-Open No. 10-12969). In Conventional Example 2,
As in the first conventional example, a nitride semiconductor laser is manufactured by the MOVPE method. A substrate 1 having sapphire A-plane as a main surface is prepared, and a buffer layer 2 of GaN is grown at a temperature of 500 ° C. on the surface of the sapphire substrate 1 to a thickness of 200 °. Subsequently, the temperature was increased to 1050 ° C.
An n-type contact layer 3 of l _0.3 Ga _0.7 N is 4 μm
It grows with the film thickness of. Subsequently, while maintaining the temperature at 1050 ° C., an n-type cladding layer 4 made of Si-doped n-type GaN is grown to a thickness of 500 °.

Next, at a temperature of 750 ° C., an active layer 5 doped with Si is grown. The active layer 5 is made of In _0.2 Ga _0.8 doped with Si at a concentration of 1 × 10 ²⁰ / cm ^3.
A well layer of N is grown to a thickness of 25 °. next,
At the same temperature, a barrier layer made of non-doped In _0.01 Ga _0.95 N is grown to a thickness of 50 °. This operation is repeated 13 times to form an active layer 5 having a multi-quantum well structure with a total film thickness of 0.1 μm by stacking wells + barrier + well +... + Barrier + well layers. Next, the first p-type layer 6 made of Mg-doped p-type Al _0.2 Ga _0.8 N is
It grows with the film thickness of. Next, the temperature was raised to 1050 ° C.
The second p-type layer 7 made of g-doped p-type GaN is
It grows with the film thickness of.

Next, at a temperature of 1050 ° C., Mg-doped Al
_A third p-type layer 8 of _0.3 Ga _0.7 N is grown to a thickness of 0.3 μm. Subsequently, at 1050 ° C., Mg-doped p
A p-type contact layer 9 of type GaN is grown to a thickness of 0.5 μm. Selective etching is performed from the p-type contact layer 9 to expose the surface of the n-type contact layer 3, and stripe-shaped electrodes are formed on the exposed surfaces of the n-type contact layer 3 and the p-type contact layer 9, respectively.

[0010]

The conventional method for growing a nitride semiconductor crystal containing indium as described above has the following problems. Although slightly different depending on the growth method, the growth apparatus, the growth conditions, and the like, generally, In evaporates at a high temperature so that Inx Ga1-x N (0 <
In the growth of X ≦ 1), the substrate temperature needs to be about 900 ° C. or less, preferably about 800 ° C. or less. On the other hand, the decomposition of NH ₃ is required high temperatures, especially in the MOVPE method in the case of using NH ₃ as a group V raw material, I
In growing AlxGa1-xN (0≤X≤1) containing no n, a substrate temperature of about 900 ° C. or more, preferably about 1000 ° C. or more is desirable. For this reason, in Conventional Example 1, at the substrate temperature of 750 ° C., the well layer of In _0.2 Ga _0.8 N
After growing an active layer 37 having a multiple quantum well structure comprising a barrier layer of _0.01 Ga _0.95 N, a p-type cap layer 38 of Mg-doped p-type Al _0.2 Ga _0.8 N is grown at a substrate temperature of 1050 ° C.

However, in Conventional Example 1, after the active layer 37 is grown at a temperature of 750 ° C., before the growth of the p-type cap layer 38 at a temperature of 1050 ° C., the growth is interrupted and the substrate is heated. Therefore, In evaporates during the temperature rise, and the active layer 37
There is a problem that the quantum well layer and the barrier layer on the top of the semiconductor device are destroyed. Further, when the substrate temperature approaches 1050 ° C., I
Ga as well as n evaporates.

On the other hand, in the conventional example 2, after the active layer 5 is grown at a substrate temperature of 750 ° C., the Mg-doped p-type Al _0.2 Ga
_A first p-type layer 6 of _0.8 N is grown, and then a second p-type layer 7 of Mg-doped p-type GaN is grown at a substrate temperature of 1050 ° C. However, in Conventional Example 2,
Normally, the first p-layer made of Mg-doped p-type Al _0.2 Ga _0.8 N is preferably grown at a substrate temperature of about 1000 ° C. or higher.
The mold layer 6 is formed at a substrate temperature of 750 ° C.
It is formed by. For this reason, the first p-type layer 6 has a problem that the crystallinity is extremely poor and the characteristics of the device are adversely affected.

In the example disclosed in Japanese Patent Application Laid-Open No. 10-27939, the p-type cap layer 38 of the first conventional example has In
The active layer made of GaN acts as a cap layer for preventing decomposition, and by growing a p-type cap layer 38 made of a p-type nitride semiconductor containing Al on the active layer, the light emission output is significantly improved. It is reported that the output of the device is reduced to about 1/3 when the p-layer in contact with the active layer is made of GaN. The cause is Alx Ga1-x N
(0 <X ≦ 1) is more likely to be p-type than GaN, and Inx Ga1-x N (0 <
X ≦ 1) is presumed to be due to the effect of suppressing decomposition, but it is also stated that the details are unknown.

In the example disclosed in Japanese Patent Application Laid-Open No. 10-12969, the output of the device is remarkably improved by forming the first p-type layer 6 of the conventional example 2 in contact with the active layer 5. I have. The cause is presumed to be the effect of suppressing the decomposition of InGaN in the active layer during the growth of the first p-type layer 6, but it is also stated that the details are unknown.

[0015] From the above problems, the object of the present invention is to
An object of the present invention is to provide a method for growing a nitride semiconductor crystal containing indium, which can stably form a semiconductor layer containing indium by crystal growth, for example, can manufacture a nitride laser having a good active layer.

[0016]

In order to achieve the above object, a method for growing a semiconductor crystal containing indium according to the present invention comprises a first step of forming at least a first nitride semiconductor layer containing In. A second step of raising the temperature of the substrate while forming a second separate nitride semiconductor layer, and a third step of forming a third nitride semiconductor layer containing no In. To the third step.

Further, another method for growing a nitride semiconductor crystal containing indium according to the present invention is a method for growing a nitride semiconductor crystal having the general formula In1-x Al1-
a first step of forming a first nitride semiconductor layer containing at least indium represented by y Ga1-xy N (0 <X ≦ 1, 0 ≦ Y <1), and a general formula In1-x Al1- y Ga
A second represented by 1-xy N (0 ≦ X <1, 0 ≦ Y ≦ 1)
A second step of raising the temperature of the substrate while forming another nitride semiconductor layer of the general formula Al1-x Ga1-x N (0 ≦ X ≦ 1)
And a third step of forming a third nitride semiconductor layer containing no In represented by the following formula: wherein the steps are performed in the order of the first to third steps.

Preferably, the first step is performed at a substrate temperature of 900 ° C. or lower, and the third step is performed at a substrate temperature of 900 ° C. or higher. Further, the first step is performed at a substrate temperature of 800 ° C. or lower, and the third step is performed at a substrate temperature of 1000 ° C. or higher.

Further, still another method for growing a nitride semiconductor crystal containing indium according to the present invention is a method for growing a nitride semiconductor crystal having the general formula In1-xA.
a barrier layer represented by l1-y Ga1-xy N (0 <X≤1, 0≤Y <1), and a general formula In1-x Al1-y Ga1-xy N
A first step of forming a single or multiple quantum well structure comprising a well layer represented by (0 <X ≦ 1, 0 ≦ Y <1), and a final layer of the single or multiple quantum well structure A second step of raising the temperature of the substrate while maintaining the same raw material supply amount as in the formation, and a nitride semiconductor layer containing no In and represented by the general formula Al1-xGa1-xN (0≤X≤1) And a third step of forming the first step, and the steps are performed in the order of the first to third steps.

According to still another method of growing a nitride semiconductor crystal containing indium according to the present invention, there is provided a first step of forming a first nitride semiconductor layer containing at least In; Second containing Al at substantially the same substrate temperature
A second step of forming a third nitride semiconductor layer, a third step of raising the temperature of the substrate, and a fourth step of forming a third nitride semiconductor layer containing Al. 4th
Are performed in the order of the steps.

Further, still another method for growing a nitride semiconductor crystal containing indium according to the present invention is a method for growing a nitride semiconductor crystal having the general formula In1-xA.
a first step of forming a first nitride semiconductor layer represented by l1-y Ga1-xy N (0 <X≤1, 0≤Y <1), and substantially the same as the first step General formula In1-x at substrate temperature
A second step of forming a second nitride semiconductor layer represented by Al1-y Ga1-x-yN (0 <X≤1, 0≤Y <1), and a third step of raising the temperature of the substrate. Process and the general formula Al1-xGa
At least a fourth step of forming a third nitride semiconductor layer represented by 1-xN (0 ≦ X ≦ 1), wherein the steps are performed in the order of the first to fourth steps. I have.

Preferably, the first step is performed at a substrate temperature of 900 ° C. or lower, and the fourth step is performed at a substrate temperature of 900 ° C. or higher. Further, the first step is performed at a substrate temperature of 800 ° C. or lower, and the fourth step is performed at a substrate temperature of 1000 ° C. or higher.

In the method for growing a semiconductor crystal containing indium of the present invention, for example, MOVPE can be used as a crystal growth method for forming a nitride semiconductor layer. In particular, a reduced pressure MOVPE method can be used.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail based on embodiments with reference to the drawings. Embodiment 1 This embodiment is an example of an embodiment of a method for growing a nitride semiconductor crystal containing indium according to the present invention. FIG.
FIG. 2 is a schematic cross-sectional view of a nitride semiconductor laser manufactured using the crystal growth method of the embodiment. In the nitride laser of FIG. 1, after forming an active layer containing In at a substrate temperature of 750 ° C., the substrate temperature is increased while forming a GaN layer to which Mg is added.
To form a GaN layer. Semiconductor crystal layers 102, 103, 104, 105, 106 of the nitride laser,
107, 114, 109, 110 and 111 are decompressed MO
The film is formed by the VPE method.

The nitride laser is formed on a sapphire substrate 101 having a C-plane as a surface at a substrate temperature of 500 ° C., an undoped GaN low-temperature growth buffer layer 102 having a thickness of 300 ° and a substrate temperature of 1050 ° C. N-type GaN contact layer 1 having a thickness of 3 μm and doped with silicon.
03, an n-type In _0.1 Ga _0.9 N layer 10 formed at a substrate temperature of 1050 ° C. and doped with silicon and having a thickness of 0.1 μm
4. An n-type Al _0.15 Ga _0.85 N cladding layer 105 formed at a substrate temperature of 1050 ° C. and doped with silicon and having a thickness of 0.4 μm, and a thickness formed at a substrate temperature of 1050 ° C. and doped with silicon. An n-type GaN light guide layer 106 having a thickness of 0.1 μm is provided.

Further, the nitride laser is further provided on the light guide layer 106 sequentially with an undoped In _{0.2 having} a thickness of 25 °.
Ga _0.8 N quantum well layer and 50 ° thick undoped I
n _{0. 05} Ga _0.95 N consisting barrier layer, a 26 cycle formed at a substrate temperature of 750 ° C. multiple quantum well structure active layer 107,
A 100-μm-thick p-type Ga formed while increasing the substrate temperature from 750 ° C. to 1050 ° C. and doped with Mg
N layer 114, formed at a substrate temperature of 1050 ° C.
-Doped p-type GaN optical guide layer 1 with a thickness of 0.1 μm
09, a 0.4 μm-thick p-type Al _0.15 Ga _0.85 N cladding layer 110 formed at a substrate temperature of 1050 ° C. and doped with Mg, and a thickness formed at a substrate temperature of 1050 ° C. and doped with Mg A p-type GaN contact layer 111 having a thickness of 0.5 μm is provided. In the nitride laser, a p-electrode 112 made of Ni (first layer) and Au (second layer), Ti (first layer) and Al (second layer) are used as electrodes.
And an n-electrode 113 made of.

In the first embodiment, when the semiconductor crystal layer of the nitride laser shown in FIG. 1 is formed by crystal growth, a multiple quantum well structure active layer 10 containing In at a substrate temperature of 750 ° C.
7, the substrate temperature is increased from 750 ° C. to 1050 ° C. while forming the p-type GaN layer 114, and then the p-type GaN optical guide layer 109 containing no In is formed at the substrate temperature of 1050 ° C. ing. As described above, in the first embodiment, the GaN layer 1 is formed after the active layer 107 containing In is formed.
Since the temperature of the substrate was raised while forming the substrate 14, the conventional example 1
As described above, In and Ga evaporate during the temperature rise, and the active layer 10
There is no problem that the quantum well layer and the barrier layer above 7 are destroyed. Also, as in Conventional Example 2, the temperature is usually 1000 ° C.
Alx G which is preferably grown at a substrate temperature of about
Since a1-xN (0 ≦ X ≦ 1) is not formed at a low temperature, a layer having poor crystallinity does not exist in contact with the active layer 107.

Embodiment 2 This embodiment is another embodiment of the method for growing a nitride semiconductor crystal containing indium according to the present invention. FIG.
FIG. 2 is a schematic cross-sectional view of a nitride semiconductor laser manufactured using the crystal growth method of the embodiment. In the nitride laser shown in FIG. 2, after forming an active layer containing In at a substrate temperature of 750 ° C., increasing the substrate temperature while forming a GaN layer to which Mg is added, and then adding Mg at a substrate temperature of 1050 ° C. An Al _0.2 Ga _0.8 N layer is formed.
Semiconductor crystal layers 102, 103, 104 of the nitride laser,
105, 106, 107, 114, 108, 109, 1
The films 10 and 111 are formed by the reduced pressure MOVPE method.

The nitride laser shown in FIG. 2 comprises a 300 ° -thick undoped GaN low-temperature growth buffer layer 102 formed at a substrate temperature of 500 ° C. and a substrate temperature of 1050 ° C. on a sapphire substrate 101 having a C-plane as a surface. And a silicon-added n-type GaN contact layer 103 having a thickness of 3 μm and a substrate temperature of 1050 ° C. and having a silicon-added thickness of 0.1 μm and an n-type In _0.1 Ga _0.9 N layer 104. , it is formed at a substrate temperature of 1050 ° C., and n-type Al _0.15 Ga _{0. 85} n cladding layer 105 having a thickness of 0.4μm which silicon is added and is formed at a substrate temperature of 1050 ° C.,
Further, an n-type GaN optical guide layer 106 having a thickness of 0.1 μm to which silicon is added is provided.

The nitride laser further includes a light guide layer 106
On top, 25 ° thick undoped In_0.2Ga
_0.8N quantum well layer and 50 ° thick undoped In
_0.05Ga _0.95Formed at a substrate temperature of 750 ° C consisting of an N barrier layer
26-period multi-quantum well structure active layer 107
Formed while increasing the plate temperature from 750 ° C to 1050 ° C
100 ° p-type GaN layer doped with Mg
114, formed at a substrate temperature of 1050 ° C.
200 mm thick p-type Al_0.2Ga_0.8N layer 10
8. Formed at a substrate temperature of 1050 ° C. and doped with Mg
0.1 μm thick p-type GaN optical guide layer 109,
Thickness formed at a plate temperature of 1050 ° C and with Mg added
0.4 μm p-type Al_0.15Ga_0.85N cladding layer 11
0, and formed at a substrate temperature of 1050 ° C., and Mg
0.5 μm-thick p-type GaN contact layer 1
11 is provided. Also, nitride lasers are used as electrodes.
And a p-electrode composed of Ni (first layer) and Au (second layer).
The pole 112 is composed of Ti (first layer) and Al (second layer).
N electrode 113 is provided.

In the second embodiment, when the semiconductor crystal layer of the nitride laser shown in FIG. 2 is formed by crystal growth, the multiple quantum well structure containing In at a substrate temperature of 750.degree. After forming the layer 107, the substrate temperature is increased from 750 ° C. to 1050 while forming the p-type GaN layer 114.
C., and then a p-type Al _0.2 Ga _0.8 N layer 108 containing no In is formed at a substrate temperature of 1050 ° C. As described above, in the second embodiment, the active layer 107 containing In is used.
After the formation of the GaN layer 114, the substrate is heated while the GaN layer 114 is being formed. The problem that the quantum well layer and the barrier layer are destroyed does not occur. Also, as in Conventional Example 2, it is usually desirable to grow at a substrate temperature of about 1000 ° C. or higher.
Since (0 ≦ X ≦ 1) is not formed at a low temperature, a layer having poor crystallinity does not exist in contact with the active layer 107.

Embodiment 3 This embodiment is still another embodiment of the method for growing a nitride semiconductor crystal containing indium according to the present invention.
FIG. 3 is a schematic cross-sectional view of a nitride semiconductor laser manufactured by using the crystal growth method of the present embodiment. In the nitride laser shown in FIG. 3, an active layer containing In is formed at a substrate temperature of 750 ° C., and thereafter, Mg-added Al is added.
_The substrate temperature is raised while forming a _0.2 Ga _0.8 N layer. Semiconductor crystal layers 102, 103, and 10 of nitride laser
4, 105, 106, 107, 118, 109, 11
0 and 111 are formed by the reduced pressure MOVPE method.

The nitride laser shown in FIG. 3 has a substrate temperature of 500 on a sapphire substrate 101 having a C-plane as a surface.
300 ° C. undoped GaN low-temperature growth buffer layer 102 having a thickness of 300 ° C., n-type GaN contact layer 103 having a thickness of 3 μm doped with silicon and having a substrate temperature of 1050 ° C., and having a substrate temperature of 1050 ° C. And 0.1 μm thick n-type In _0.1 Ga doped with silicon
_0.9 N layer 104, is formed at a substrate temperature of 1050 ° C., and a thickness of 0.4μm which silicon is added n-type Al _0.15 Ga
_{It has a 0.85} N cladding layer 105 and an n-type GaN optical guiding layer 106 formed at a substrate temperature of 1050 ° C. and having a thickness of 0.1 μm to which silicon is added.

The nitride laser further includes a light guide layer 106
On top, 25 ° thick undoped In_0.2Ga
_0.8N quantum well layer and 50 ° thick undoped In
_0.05Ga _0.95Formed at a substrate temperature of 750 ° C consisting of an N barrier layer
26-period multi-quantum well structure active layer 107
Formed while increasing the plate temperature from 750 ° C to 1050 ° C
200 μm thick p-type Al_0.2
Ga_0.8N layer 118, formed at a substrate temperature of 1050 ° C.
A 0.1 μm-thick p-type GaN optical gas doped with Mg;
Layer 109, formed at a substrate temperature of 1050 ° C.
0.4 μm-thick p-type Al to which g has been added_0.15Ga_0.85
N clad layer 110 and formed at substrate temperature of 1050 ° C
P-type Ga doped with Mg and having a thickness of 0.5 μm.
An N contact layer 111 is provided. Nitride lasers
Electrodes made of Ni (first layer) and Au (second layer)
P electrode 112, Ti (first layer) and Al (second layer).
) Is provided.

In the third embodiment, the nitride laser shown in FIG.
When forming the semiconductor crystal layer by crystal growth,
As in the first and second embodiments, the substrate temperature is 750.
Forming a multiple quantum well structure active layer 107 containing In at 107 ° C.
After that, p-type Al_0.2Ga_0.8While forming the N layer 118
The substrate temperature is increased from 750 ° C. to 1050 ° C. This
As described above, in the third embodiment, the active layer 107 containing In is used.
After forming Al _0.2Ga_0.8While forming N layer
Since the plate is heated, the first embodiment and the first embodiment
As in the case of the conventional example 2, In and Ga are
Evaporation breaks the quantum well layer and barrier layer above the active layer 107.
There is no problem of being destroyed. Also, as in Conventional Example 2,
Alx Ga1-x N (0
≦ X ≦ 1) The question that the layer exists in contact with the active layer 107
There is no title.

Embodiment 4 This embodiment is still another embodiment of the method for growing a nitride semiconductor crystal containing indium according to the present invention.
FIG. 6 is a schematic cross-sectional view of a nitride semiconductor laser manufactured using the crystal growth method of the present embodiment. In the nitride laser shown in FIG. 6, after forming an active layer containing In at a substrate temperature of 750 ° C., In _0.1 Ga _0.9 containing Mg is added.
The substrate temperature is increased while forming the N layer, and thereafter, a GaN layer to which Mg is added at a substrate temperature of 1050 ° C. is formed. Semiconductor crystal layers 102, 103, and 10 of nitride laser
4, 105, 106, 107, 115, 109, 11
0 and 111 are formed by the reduced pressure MOVPE method.

The nitride laser shown in FIG. 6 has a substrate temperature of 500 on a sapphire substrate 101 having a C-plane as a surface.
300 ° C. undoped GaN low-temperature growth buffer layer 102 having a thickness of 300 ° C., n-type GaN contact layer 103 having a thickness of 3 μm doped with silicon and having a substrate temperature of 1050 ° C., and having a substrate temperature of 1050 ° C. And 0.1 μm thick n-type In _0.1 Ga doped with silicon
_0.9 N layer 104, is formed at a substrate temperature of 1050 ° C., and a thickness of 0.4μm which silicon is added n-type Al _0.15 Ga
_{It has a 0.85} N cladding layer 105 and an n-type GaN optical guiding layer 106 formed at a substrate temperature of 1050 ° C. and having a thickness of 0.1 μm to which silicon is added.

The nitride laser further includes a light guide layer 106
On top, 25 ° thick undoped In_0.2Ga
_0.8N quantum well layer and 50 ° thick undoped In
_0.05Ga _0.95Formed at a substrate temperature of 750 ° C consisting of an N barrier layer
26-period multi-quantum well structure active layer 107
Formed while increasing the plate temperature from 750 ° C to 1050 ° C
P-type In with a thickness of 100 °_0.1
Ga_0.9An N layer 115 formed at a substrate temperature of 1050 ° C.
A 0.1 μm-thick p-type GaN optical gas doped with Mg;
Layer 109, formed at a substrate temperature of 1050 ° C.
0.4 μm-thick p-type Al to which g has been added_0.15Ga_0.85
N clad layer 110 and formed at substrate temperature of 1050 ° C
P-type Ga doped with Mg and having a thickness of 0.5 μm.
An N contact layer 111 is provided. Nitride lasers
Electrodes made of Ni (first layer) and Au (second layer)
P electrode 112, Ti (first layer) and Al (second layer).
) Is provided.

In the fourth embodiment, when the semiconductor crystal layer of the nitride laser shown in FIG. 6 is formed by crystal growth, the multiple quantum well structure active layer 10 containing In at a substrate temperature of 750 ° C.
After forming 7, the substrate temperature is increased from 750 ° C. to 1050 ° C. while forming the p-type In _0.1 Ga _0.9 N layer 115, and then the p-type GaN optical guide layer 109 is formed at the substrate temperature of 1050 ° C. . The above In _0.1 Ga _0.9 N
The layer 115 is formed while increasing the temperature of the substrate from 750 ° C. to 1050 ° C., but the amount of In incorporated into the epitaxial growth layer strongly depends on the substrate temperature, and the coefficient of the incorporated In increases with the substrate temperature. It becomes smaller as Therefore, actually, the composition of the In _0.1 Ga _0.9 N layer 115 is In _0.1 Ga _0.8 N as described at the lower portion, but is close to GaN at the upper portion. When the substrate is heated while forming an Inx Ga1-x N (0 <X <1) layer instead of a GaN layer, the substrate is formed at a high temperature in the first half of the temperature rise by incorporating In into the crystal and in the second half of the temperature rise. By doing
It is possible to raise the temperature of the substrate while maintaining the crystal quality.

As described above, Embodiment 4 includes In.
After forming the active layer 107, _0.1Ga_0.9N layer 1
Since the temperature of the substrate is raised while forming No. 15, the embodiment
As in Example 1 to Embodiment 3, as in Conventional Example 1,
During the temperature rise, In and Ga evaporate, and the upper quantum
There is no problem that the well layer and the barrier layer are destroyed. Ma
In addition, Al with poor crystallinity grown at a low temperature as in Conventional Example 2
The x Ga1-x N (0 ≦ X ≦ 1) layer contacts the active layer 107
There is no problem of existence.

Embodiment 5 This embodiment is still another embodiment of the method for growing a nitride semiconductor crystal containing indium according to the present invention.
FIG. 7 is a schematic cross-sectional view of a nitride semiconductor laser manufactured by using the crystal growth method of the present embodiment. In the nitride laser shown in FIG. 7, an active layer containing In is formed at a substrate temperature of 750.degree.
After the formation of the Al _0.2 Ga _0.8 N layer to which Mg is added, the growth is interrupted and the substrate is heated to form an Al _0.2 Ga _0.8 N layer to which Mg is added at a substrate temperature of 1050 ° C. Semiconductor crystal layers 102, 103, 104, 105 of the nitride laser,
106, 107, 116, 118, 109, 110, 1
11 is formed by a reduced pressure MOVPE method.

The nitride laser shown in FIG. 7 has a substrate temperature of 500 on a sapphire substrate 101 having a C-plane as a surface.
300 ° C. undoped GaN low-temperature growth buffer layer 102 having a thickness of 300 ° C., n-type GaN contact layer 103 having a thickness of 3 μm doped with silicon and having a substrate temperature of 1050 ° C., and having a substrate temperature of 1050 ° C. And 0.1 μm thick n-type In _0.1 Ga doped with silicon
_0.9 N layer 104, is formed at a substrate temperature of 1050 ° C., and a thickness of 0.4μm which silicon is added n-type Al _0.15 Ga
_{It has a 0.85} N cladding layer 105 and an n-type GaN optical guiding layer 106 formed at a substrate temperature of 1050 ° C. and having a thickness of 0.1 μm to which silicon is added.

The nitride laser further includes a light guide layer 106
On top, 25 ° thick undoped In_0.2Ga
_0.8N quantum well layer and 50 ° thick undoped In
_0.05Ga _0.95Formed at a substrate temperature of 750 ° C consisting of an N barrier layer
26-period multi-quantum well structure active layer 107
Thickness formed at a plate temperature of 750 ° C and with Mg added
50 ° p-type Al_0.2Ga_0.8N layer 116, substrate temperature 1
Thickness 100 formed at 050 ° C. and doped with Mg
Ｐ p-type Al_0.2Ga_0.8N layer 108, substrate temperature 105
Formed at 0 ° C. and added with Mg to a thickness of 0.1 μm
At a substrate temperature of 1050 ° C.
0.4 μm thick p-type formed and doped with Mg
Al_0.15Ga_0.85N cladding layer 110 and substrate temperature
Thickness formed at 1050 ° C. and added with Mg
A 5 μm p-type GaN contact layer 111 is provided.
The nitride laser uses Ni (first layer) and A
p (electrode) 112 made of u (second layer), Ti (first layer)
And an n-electrode 113 made of Al (second layer).
You.

In the fifth embodiment, when the semiconductor crystal layer of the nitride laser shown in FIG. 7 is formed by crystal growth, the active layer 10 having a multiple quantum well structure containing In at a substrate temperature of 750 ° C.
7, followed by p-type Al _0.2 G at a substrate temperature of 750 ° C.
After forming the a _0.8 N layer 116, the growth is temporarily stopped,
The temperature of the substrate is raised from 750 ° C. to 1050 ° C., and thereafter, at a substrate temperature of 1050 ° C., the p-type Al _0.2 Ga _0.8 N layer 108 is formed.
Is formed. In this case, although the temperature of the substrate is raised by suspending the growth, the temperature is raised by the active layer 1 containing In.
07 at the same substrate temperature as the p-type Al _0.2 Ga _0.8 N layer 116.
Is performed after the formation.

Al is less likely to evaporate than Ga. According to the experiments by the inventors, after forming the active layer 107 containing In, at a substrate temperature the same as when the active layer 107 containing In is subsequently formed, it is assumed that Al is formed. Alx Ga1-x N (0 <
It has been found that the formation of the layer (X ≦ 1) has the effect of preventing the evaporation of the active layer 107 containing In when the substrate is subsequently heated (see Japanese Patent Application No. 9-213273). ). Therefore, similarly to the first to fourth embodiments, the problem is that In and Ga evaporate during the temperature rise and the quantum well layer and the barrier layer above the active layer 107 are destroyed as in the first conventional example. Does not occur. Also, p-type Al formed at low temperature
_Since the thickness of the _0.2 Ga _0.8 N layer 116 is as thin as 50 °, AlxG having poor crystallinity grown at a low temperature as in Conventional Example 2 is used.
The adverse effect on device characteristics due to the existence of the a1-xN (0 ≦ X ≦ 1) layer in contact with the active layer 107 is small.

In the fifth embodiment, the substrate temperature and the p-type Al _0.2 Ga
The substrate temperature at the time of forming the _0.8 N layer 116 does not need to be exactly the same, and the substrate temperature at the time of forming the p-type Al _0.2 Ga _0.8 N layer 116 is +50 relative to the substrate temperature at the time of forming the active layer 107 containing In. If the temperature is lower than about ° C, it can be considered that they are substantially the same.

In Japanese Patent Application Laid-Open No. 10-27939, the p-type cap layer 38 shown in Conventional Example 1 has a function as a cap layer for preventing the active layer made of InGaN from being decomposed, and is in contact with the active layer. It is stated that when the p-layer is made of GaN, the output of the device is reduced to about 1/3. Japanese Patent Application Laid-Open No. 10-12969 also states that the first p-type layer 6 shown in Conventional Example 2 is formed in contact with the active layer 5 to significantly improve the output of the element.
However, in our experiments, the p-type Al _0.2 Ga _{0. 8} N layer 108 shown in Embodiment 2, as shown in Conventional Examples 1 and 2, to be formed in contact with the active layer In such a case, there is a problem as described in the above-mentioned "Problem to be Solved by the Invention", but no effect of improving the light output of the device was found.

In the embodiments of the present invention, a nitride laser formed on a sapphire C-plane substrate has been described as an example. However, the present invention is applied to the first to fifth embodiments.
However, the present invention is not limited to the epitaxial layer structure shown in the above, and can be applied to nitride lasers having any epitaxial layer structure without departing from the spirit of the present invention. In addition, the present invention can be applied to not only a nitride laser formed on a sapphire C-plane substrate but also a nitride laser formed on a sapphire substrate having a surface other than the C-plane as a surface. Can be done. Furthermore, in a nitride laser formed on a substrate other than the sapphire substrate,
The present invention can be implemented without hindrance. Furthermore, not only nitride lasers but also nitride light-emitting diodes
The present invention can be implemented without any problem in other nitride light emitting devices.

[0049]

According to the present invention, the temperature of the substrate is increased while forming a first nitride semiconductor layer containing at least In and then forming another second nitride semiconductor layer. By forming the third nitride semiconductor layer that does not include the third nitride semiconductor layer, it is possible to increase the temperature of the first nitride semiconductor layer while increasing the temperature of the first nitride semiconductor layer.
There is no problem that a is evaporated and the quantum well layer and the barrier layer above the active layer are destroyed. Further, there is no problem that the third nitride semiconductor layer grown at a low temperature and having poor crystallinity exists in contact with the active layer as in the related art.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a nitride laser manufactured using a crystal growth method according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a nitride laser manufactured by using the crystal growth method according to the second embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a nitride laser manufactured by using a crystal growth method according to a third embodiment of the present invention.

FIG. 4 is a schematic sectional view of a nitride laser manufactured by using the conventional crystal growth method of Conventional Example 1.

FIG. 5 is a schematic sectional view of a nitride laser manufactured by using the conventional crystal growth method of Conventional Example 2.

FIG. 6 is a schematic sectional view of a nitride laser manufactured by using the crystal growth method according to the fourth embodiment of the present invention.

FIG. 7 is a schematic sectional view of a nitride laser manufactured by using the crystal growth method according to the fifth embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 Substrate having sapphire A-plane as main surface 2 Buffer layer 3 n-type contact layer made of Si-doped Al _0.3 Ga _0.7 N 4 n-type clad layer made of Si-doped n-type GaN 5 From Si-doped multiple quantum well structure Active layer 6 Mg-doped p-type Al _0.2 Ga _0.8 N first p-type layer 7 Mg-doped p-type GaN second p-type layer 8 Mg-doped Al _0.3 Ga _0.7 N third p-type Layer 9 Mg-doped p-type contact layer 31 made of p-type GaN 31 Sapphire substrate whose main surface is A 32 Buffer layer made of GaN 33 n-type contact layer made of Si-doped n-type GaN 34 Si-doped In ₀ .Ga _0.9 N Crack preventing layer 35 n-type optical confinement layer made of Si-doped n-type Al _0.3 Ga _0.7 N 36 n-type optical guide layer made of Si-doped n-type GaN 37 Active layer having a multiple quantum well structure 38 p-type cap layer made of Mg-doped p-type Al _0.2 Ga _0.8 N 39 p-type optical guide layer made of Mg-doped p-type GaN 40 p-type made of Mg-doped Al _0.3 Ga _0.7 N Optical confinement layer 41 P-type contact layer made of Mg-doped p-type GaN 42 Positive electrode containing Ni and Au 43 Negative electrode made of Ti and Al 101 C-plane sapphire substrate 102 GaN low-temperature growth buffer layer 103 n-type In _0.2 Ga _0.8 N Contact layer 104 n-type In _0.1 Ga _0.9 N layer 105 n-type Al _0.15 Ga _0.85 N layer 106 n-type GaN optical guide layer 107 In _0.2 Ga _0.8 N / In _0.05 Ga _0.95 N multiple quantum well active layer 108 formed at high temperature p-type Al _0.2 Ga _0.8 N layer 109 p-type GaN optical guide layer 110 p-type Al _0.15 Ga _0.85 N cladding layer 11 p-type In _0.2 Ga _0.8 N contact layer 112 Ni and consists of Au p electrode 113 Ti and consists Al n electrode 114 p-type GaN layer 115 p-type In _0.1 Ga _0.9 N layer 116 p-type are formed at a low temperature Al _0.2 Ga _0.8 N layer 118 p-type Al _0.2 G formed while heating the substrate
a _0.8 N layer

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference)

Claims (11)

[Claims] A first step of forming a first nitride semiconductor layer containing at least In; a second step of raising a temperature of a substrate while forming a second nitride semiconductor layer; A third step of forming a third nitride semiconductor layer containing no indium, and performing the steps in the order of the first to third steps. 2. The general formula In1-x Al1-y Ga1-xy N
A first step of forming a first nitride semiconductor layer containing at least indium represented by (0 <X ≦ 1, 0 ≦ Y <1), and a general formula In1-x Al1-y Ga1-xy N (0 ≦ X <1,0
≦ Y ≦ 1), a second step of raising the temperature of the substrate while forming a second separate nitride semiconductor layer, and a general formula of Al1-x Ga1-x N (0 ≦ X ≦ 1) Represented by
A third step of forming a third nitride semiconductor layer not containing In, and a method of growing a nitride semiconductor crystal containing indium, wherein the steps are performed in the order of the first to third steps. 3. The nitride semiconductor crystal containing indium according to claim 2, wherein the first step is performed at a substrate temperature of 900 ° C. or lower, and the third step is performed at a substrate temperature of 900 ° C. or higher. Growth method. 4. The nitride semiconductor crystal containing indium according to claim 2, wherein the first step is performed at a substrate temperature of 800 ° C. or lower, and the third step is performed at a substrate temperature of 1000 ° C. or higher. Growth method. 5. The general formula In1-x Al1-y Ga1-xy N
A barrier layer represented by (0 <X ≦ 1, 0 ≦ Y <1) and a general formula In1-x Al1-y Ga1-xy N (0 <X ≦ 1, 0 ≦ Y
A first step of forming a single or multiple quantum well structure comprising a well layer represented by <1), while maintaining the same raw material supply amount as in forming the final layer of the single or multiple quantum well structure A second step of raising the temperature of the substrate, and represented by a general formula Al1-x Ga1-x N (0 ≦ X ≦ 1),
And a third step of forming a nitride semiconductor layer containing no In. The method of growing a nitride semiconductor crystal containing indium, the method being performed in the order of the first to third steps. 6. A first step of forming a first nitride semiconductor layer containing at least In, and forming a second nitride semiconductor layer containing Al at substantially the same substrate temperature as in the first step. A third step of raising the temperature of the substrate, and a fourth step of forming a third nitride semiconductor layer containing Al, in the order of the first to fourth steps. A method of growing a nitride semiconductor crystal containing indium. 7. The formula In1-x Al1-y Ga1-xy N
A first step of forming a first nitride semiconductor layer represented by (0 <X ≦ 1, 0 ≦ Y <1); and a substrate having substantially the same general formula In1-
x Al1-y Ga1-x-yN (0 <X≤1, 0≤Y <1), a second step of forming a second nitride semiconductor layer, and a third step of raising the temperature of the substrate. And a process represented by the general formula: Al1-x Ga1-x N (0 ≦ X ≦ 1)
And a fourth step of forming a third nitride semiconductor layer. The method of growing a nitride semiconductor crystal containing indium, the method being performed in the order of the first to fourth steps. 8. The indium-containing nitride semiconductor crystal according to claim 7, wherein the first step is performed at a substrate temperature of 900 ° C. or lower, and the fourth step is performed at a substrate temperature of 900 ° C. or higher. Growth method. 9. The nitride semiconductor crystal containing indium according to claim 7, wherein the first step is performed at a substrate temperature of 800 ° C. or lower, and the fourth step is performed at a substrate temperature of 1000 ° C. or higher. Growth method. 10. The nitride semiconductor layer is formed by using a metal organic chemical vapor deposition method.
The method for growing a nitride semiconductor crystal containing indium according to any one of the above. 11. The nitride semiconductor crystal containing indium according to claim 1, wherein the nitride semiconductor layer is formed by using reduced pressure metal organic chemical vapor deposition. Growth method.