JPH10261816A - Semiconductor light emitting element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method by which a semiconductor light emitting element which can highly efficiently emit light can be manufactured by making the growing temperature of an InGaN crystal having a required In composition higher. SOLUTION: A semiconductor light emitting element is formed by laminating a nitride semiconductor layer made of GaN, Inx Ga1-x N, Aly Ga1-y N, etc., containing an MQW active layer 4 composed of a nondoped InGaN, well layer and a nondoped GaN barrier layer upon the (0001)c-face of a 6H-SiC (0001)c substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a GaN-based nitride semiconductor (for example, GaN, In _x Ga ₁ -xN, Al _y G
a _1-y N) and a method for manufacturing the same.

[0002] GaN-based light emitting diodes have emission wavelengths from the green region to the ultraviolet region and are expected as light sources for displays. GaN-based semiconductor lasers have emission wavelengths from the blue region to the ultraviolet region. Although sapphire (Al ₂ O ₃ ) has been expected as a light source capable of further improving the storage density of a digital information recording device such as a magneto-optical disk using a red semiconductor laser. There is a problem that the substrate cannot be cleaved, and this must be solved.

[0003]

2. Description of the Related Art At present, a semiconductor light emitting device of the type described above includes:
Sapphire having a plane index of (0001) is used as a substrate, a high-quality GaN-based crystal can be grown on the substrate, and a low-cost, large-area one can be easily obtained. Although there are many advantages, such as that, the (0001) sapphire substrate does not have a cleavage plane perpendicular to the surface, so that cleavage cannot be performed with good reproducibility.

[0004] This is a particular problem in device isolation or fabrication of a laser resonator which is usually realized by using cleavage.

At present, element separation is performed by using a dicing saw.
Since a width of 00 [μm] to 300 [μm] is required,
There is a problem that waste due to this cutting margin is large.

[0006] In addition, a dry cavity
Although a method using an etching method is employed, there is a problem that flatness and verticality are poor.

Therefore, as a substrate replacing sapphire,
Attention has been paid to a 6H-SiC (0001) _Si substrate having a vertical cleavage plane, and an LED (light emittin)
2. Description of the Related Art A semiconductor light emitting device for which g diode is manufactured is known.

[0008] The (0001) plane of 6H-SiC has polarity, and includes a Si plane in which Si atoms are exposed and a C plane in which C atoms are exposed, and has a (0001) plane. S
In the iC substrate, if the front surface is Si, the back surface is the C surface.

The substrate of the GaN-based semiconductor light emitting device is S
An i-plane is used, which, when using a Si plane, is GaN
This is because a flat surface of the system crystal can be easily obtained.

Normally, when the C plane is used, only a surface with severe irregularities can be obtained, and no means for obtaining a flat surface has been realized.

[0011]

SUMMARY OF THE INVENTION 6H-SiC (000
1) One of the problems in the case of using a _Si substrate is that the growth temperature of the InGaN crystal serving as the light emitting layer is low, so that a good crystal is not obtained, and the luminous efficiency is low.

As the growth temperature of the InGaN crystal becomes higher, a better crystal is obtained and the luminous efficiency is improved. However, in such a case, a desired In composition cannot be obtained.

Incidentally, while the growth temperature of GaN or AlGaN is about 1000 ° C., the growth temperature of InGaN is about 800 ° C.

FIG. 5 is a diagram showing the relationship between the supply amount of In and the In composition of the InGaN crystal when the growth temperature is kept constant. The horizontal axis represents the In composition in the source gas, and the vertical axis represents the crystal. The In composition in each is taken.

As can be seen from the figure, even if the supply amount of In is increased, the amount of In in the crystal is saturated without increasing.

FIG. 6 is a graph showing the relationship between the growth temperature and the maximum In composition taken into the crystal. The horizontal axis indicates the growth temperature, and the vertical axis indicates the In composition in the crystal.

As can be seen from the figure, the lower the growth temperature,
It is observed that In is easily taken into the crystal.

From the data shown in FIGS. 5 and 6, it can be understood that there is an upper limit to the growth temperature when a crystal having a required In composition is grown, and the growth temperature cannot be higher than the upper limit. .

According to the inventor's knowledge, at the above-mentioned upper limit temperature, I
Even if an nGaN crystal is grown, its crystallinity is poor, and thus the luminous efficiency is low.

In the present invention, InG having a required In composition
It is possible to increase the growth temperature of the aN crystal and obtain a semiconductor light emitting device having high luminous efficiency.

[0021]

According to the present invention, 6H-
An InGaN crystal layer having a flat surface can be formed on a substrate having a (0001) _C- plane as a surface in a SiC single crystal, and its principle is based on two findings by the present inventors. Has become.

The first finding was that 6H-SiC was used as the substrate.
Instead of using (0001) _si , 6H-SiC (000
1) When _C is used, the maximum amount of In incorporated into the InGaN crystal can be increased.

FIG. 1 shows the relationship between the growth temperature of a crystal and the maximum In composition taken in the crystal.
When using a (0001) _si substrate and 6H-SiC
FIG. 3 is a diagram showing a comparison using a (0001) _C substrate.

According to the figure, at the same growth temperature, the maximum amount of In incorporated in the crystal is about twice as large in the (0001) _C substrate as in the (0001) _si substrate. That will be taken care of.

In other words, when a crystal having the same In composition is grown by using the (0001) _C substrate,
By increasing the growth temperature by about 60 ° C., it is possible to obtain a good quality crystal.

The second finding is that an AlGaN crystal is grown on the first layer, or an AlN crystal is grown on the first layer and a GaN crystal is grown on the second layer. By growing the layer at a high temperature of 1200 [° C.], even when a 6H—SiC (0001) _C substrate is used, the surface becomes similar to that when a 6H—SiC (0001) _si substrate is used. This means that a flat InGaN crystal can be grown, and such an effect can be obtained by increasing the growth temperature to 1100 [° C.] or more, preferably 120 ° C., according to experiments.
It can be obtained by setting the temperature to 0 [° C.] or more.

The growth temperature of 1200 ° C. is 150 ° C. higher than 1050 ° C., which is a typical growth temperature when a sapphire (0001) substrate or 6H—SiC (0001) _si substrate is used. In the case where each of the substrates is used, the temperature is not adopted.

By combining the two findings,
Compared with the conventional technique using a 6H-SiC (0001) _si substrate, In has a high quality and a flat surface at a high temperature.
It has become possible to grow GaN crystals.

As described above, in the semiconductor light emitting device and the method of manufacturing the same according to the present invention, (1) a 6H-SiC single crystal substrate (for example, 6H-SiC
A light emitting layer composed of In _x Ga ₁ -xN laminated on the (0001) _C plane in the (0001) _C substrate 1) (for example, an MQW active layer 4 composed of a non-doped InGaN well layer and a non-doped GaN barrier layer) GaN-based nitride semiconductor layer (e.g. GaN _{containing, in x Ga 1-x N} , Al y
Ga _1-y N), or

(2) Al _y Ga _1-y N (0 <y <1) on (0001) _C plane in 6H—SiC single crystal substrate
After forming the layer at a temperature of 1100 ° C. or more, another Ga
Or forming a step of forming an N-based nitride semiconductor layer, or

(3) An AlN layer and a GaN layer are formed on the (0001) _C plane of the 6H-SiC single crystal substrate by 1100.
Forming a layer at a temperature of [° C.] or more and then forming another GaN-based nitride semiconductor layer.

By adopting the above-mentioned means, the InGaN crystal can be grown at a high growth temperature while maintaining the desired In composition. Therefore, the crystal is of good quality and has a flat surface. And a GaN-based semiconductor light emitting device with high luminous efficiency can be realized.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a cutaway front view of a main part showing a semiconductor light emitting device at a key point in a process for explaining a first embodiment of the present invention, and FIG. Hereinafter, description will be made with reference to these figures. Here, the semiconductor laser is targeted.

See FIG. 2 2- (1) Metalorganic vapor phase growth
6H-SiC (0001) _C substrate 1 by applying the MOVPE (or phaseepitaxy: MOVPE) method.
The cladding layer 2, the optical confinement layer 3, and the MQW (multi
i quantum well) An active layer 4, a light confinement layer 5, a cladding layer 6, and a contact layer 7 are formed.

The main data on each semiconductor layer grown here is as follows.

Regarding the cladding layer 2 Material: n-AlGaN Al composition: 10 [%] Thickness: 1.0 [μm] Impurity concentration: 1 × 10 ¹⁸ [cm ^-3 ] Growth temperature: 1200 [° C.]

About the light confinement layer 3 Material: non-doped GaN Thickness: 0.1 [μm] Growth temperature: 870 [° C.]

Regarding MQW active layer 4 Number of QW layers: 3 Well layers Material: non-doped InGaN In composition: 15 [%] Thickness: 25 [Å] Growth temperature: 870 [° C.] Barrier layer Material: non-doped GaN Thickness: 25 [Å] Growth temperature: 870 [° C]

Light confinement layer 5 Material: non-doped GaN Thickness: 0.1 [μm] Growth temperature: 870 [° C.]

Regarding the cladding layer 6 Material: p-AlGaN Al composition: 10 [%] Thickness: 0.4 [μm] Impurity concentration: 5 × 10 ¹⁷ [cm ^-3 ] Growth temperature: 1050 [° C.]

About contact layer 7 Material: p-GaN Thickness: 0.1 [μm] Impurity concentration: 2 × 10 ¹⁸ [cm ⁻³ ] Growth temperature: 1050 [° C.]

FIG. 3 3- (1) Resist process in lithography technology and
By applying a dry etching method using a chlorine-based gas as an etching gas, etching is performed to generate a step that reaches the inside of the cladding layer 2 from the surface of the contact layer 7 to expose a part of the cladding layer 2. Let it.

In this case, since the (1-100) cleavage plane of 6H-SiC and each epitaxially grown semiconductor layer is used as a laser resonator, the extending direction of the step is [1].
−100] direction.

3- (2) By applying a resist process, a vacuum deposition method, and a lift-off method in the lithography technique, [1-100] is formed on the lower side of the step, that is, on the cladding layer 2. An n-side electrode 8 extending in the direction is formed, and a p-side electrode 9 extending in the [1-100] direction is formed above the step, that is, on the contact layer 7.

Here, the n-side electrode 8 has a thickness of, for example, 20
00 [Å] / 1000 [Å] / 3000 [Å] Ti /
The P-side electrode may be made of Ni / Au having a thickness of, for example, 2000 [の] / 3000 [Å].

3- (3) A laser resonator is formed by cleaving the wafer on the (1-100) plane to complete the laser cavity.

FIG. 4 is a fragmentary front view showing a semiconductor light emitting device at a key step for explaining a second embodiment of the present invention. The following description will be made with reference to these drawings. I do. Here, the semiconductor laser is also targeted.

Referring to FIG. 4, 4- (1) 6H-SiC (0
001) Buffer layer 12 and buffer layer 1 on _C substrate 11
3, a cladding layer 14, a light confinement layer 15, an MQW active layer 16, a light confinement layer 17, a cladding layer 18, and a contact layer 19 are formed.

The main data on each semiconductor layer grown here is as follows.

Regarding the buffer layer 12 Material: non-doped AlN Thickness: 200 [Å] Growth temperature: 1200 [° C.]

Regarding the buffer layer 13 Material: n-GaN Impurity concentration: 1 × 10 ¹⁸ [cm ⁻³ ] Thickness: 1.0 [μm] Growth temperature: 1200 [° C.]

Regarding the cladding layer 14 Material: n-AlGaN Al composition: 10 [%] Thickness: 0.2 [μm] Impurity concentration: 1 × 10 ¹⁸ [cm ^-3 ] Growth temperature: 1200 [° C.]

Light confinement layer 15 Material: non-doped GaN Thickness: 0.1 [μm] Growth temperature: 870 [° C.]

About MQW Active Layer 16 Number of QW layers: 3 well layers Material: non-doped InGaN In composition: 15 [%] Thickness: 25 [Å] Growth temperature: 870 [° C.] Barrier layer Material: non-doped GaN Thickness: 25 [Å] Growth temperature: 870 [° C]

Light Confinement Layer 17 Material: Non-doped GaN Thickness: 0.1 [μm] Growth Temperature: 870 [° C.]

Regarding the cladding layer 18 Material: p-AlGaN Al composition: 10 [%] Thickness: 0.2 [μm] Impurity concentration: 5 × 10 ¹⁷ [cm ⁻³ ] Growth temperature: 1050 [° C.]

About the contact layer 19 Material: p-GaN Thickness: 0.4 [μm] Impurity concentration: 2 × 10 ¹⁸ [cm ⁻³ ] Growth temperature: 1050 [° C.]

Although not shown, a semiconductor light emitting device is completed through the same steps as those of the first embodiment. That is, the contact layer 1 is formed by applying a resist process in the lithography technique and a dry etching method using a chlorine-based gas as an etching gas.
Etching is performed to generate a step that reaches the inside of the buffer layer 13 from the surface of the buffer layer 9 to expose a part of the buffer layer 13.

4- (3) By applying a resist process, a vacuum deposition method, and a lift-off method in the lithography technique, the lower side of the step, ie, the buffer layer 13
An n-side electrode is formed on the upper side, and a p-side electrode is formed on the upper side of the step, that is, on the contact layer 19.

4- (4) A laser resonator is formed by cleaving the wafer on the (1-100) plane to complete the laser cavity.

[0061]

According to the semiconductor light emitting device and the method for manufacturing the same according to the present invention, (000) in a 6H-SiC single crystal substrate is used.
1) G including a light emitting layer made of In _x Ga _1-x N on the _C plane
An aN-based nitride semiconductor layer is formed by lamination.

By adopting the above configuration, an InGaN crystal can be grown at a high growth temperature while maintaining a desired In composition, and therefore, the crystal is of good quality and has a flat surface. And a GaN-based semiconductor light emitting device with high luminous efficiency can be realized.

[Brief description of the drawings]

FIG. 1 shows the growth temperature of the crystal and the maximum
Regarding the relationship with the In composition, 6H—SiC (0001)
_siWhen a substrate is used, and when 6H-SiC (0001)
_CFIG. 4 is a diagram showing a comparison between cases in which a substrate is used.

FIG. 2 is a fragmentary front view showing a semiconductor light-emitting element at a key step in the process for describing Embodiment 1 of the present invention.

FIG. 3 is a fragmentary perspective view showing a semiconductor light emitting device at a key point in the process for describing Embodiment 1 of the present invention.

FIG. 4 is a fragmentary front view showing a semiconductor light emitting device at a key point in a process for explaining a second embodiment of the present invention.

FIG. 5 shows the supply amount of In and I when the growth temperature is kept constant.
FIG. 3 is a diagram illustrating a relationship with an In composition of an nGaN crystal.

FIG. 6 is a diagram showing a relationship between a growth temperature and a maximum In composition taken into a crystal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Cladding layer 3 Optical confinement layer 4 MQW active layer 5 Optical confinement layer 6 Cladding layer 7 Contact layer 8 N side electrode 9 P side electrode

Claims (3)

[Claims] 1. The method according to claim 1, wherein (000) in a 6H-SiC single crystal substrate is used.
1) A semiconductor light emitting device comprising a GaN-based nitride semiconductor layer including a light emitting layer made of In _x Ga ₁ -xN laminated on a _C- plane. 2. The method according to claim 1, wherein (000) in a 6H-SiC single crystal substrate.
1) An Al _y Ga _1-y N (0 <y <1) layer on the _C- plane
Forming a GaN-based nitride semiconductor layer at a temperature of at least 00 [° C.] and then forming another GaN-based nitride semiconductor layer. 3. The method according to claim 1, wherein the (000)
1) Conductive light emission comprising a step of forming an AlN layer and a GaN layer on a _C- plane at a temperature of 1100 ° C. or more and forming another GaN-based nitride semiconductor layer. Device manufacturing method.