JPH0522677B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on liquid phase epitaxial growth.
This invention relates to improvements in the manufacturing method of GaAlAs light emitting devices.

In recent years, there has been a strong demand for highly efficient light emitting elements for use in optical communications or outdoor displays.
GaAlAs is a semiconductor material for high-efficiency light emitting devices.
It is known that the system has the best characteristics.
The Ga _1-x Al _x As mixed crystal has a direct transition type band structure from the composition x = 0 to around x = 0.4, and has a band structure of 6500 Å to 9000 Å.
Highly efficient light emission can be obtained between .
In the case of Ga _1-x Al _x As mixed crystal, the band gap (in Eg
It is known that the relationship between eV) and composition (x) is approximately expressed by the following relational expression.

Eg (x) = 1.424 + 1.247x ₍ ⁰ _{< x} Al _x As layer and an n-type Ga _1-y Al _y As layer with a wide band gap E ² _g (E ² _g > E ¹ _g ) that is transparent to this wavelength under the relationship y>x. It has a structure in which it grows sequentially.

Since light emission occurs in the P-type GaAlAs layer, the emission wavelength depends on the composition (x) of the P-type layer.

A typical red light-emitting element with an emission wavelength of 6600 Å is composed of a P-type layer with a composition x=0.35 and an N-type layer with a composition y=0.6 to 0.8.

In the conventional technology, a horizontal slide boat composed of two solutions, a P-type growth solution 4 and an N-type growth solution 5, as shown in FIG. A method has been adopted to do so. The disadvantages of this method are that after growing the P-type layer, the substrate crystal is once separated from the growth solution, and that various defects are introduced near the P-N interface due to scratches caused by sliding the substrate crystal. However, deterioration and variation in characteristics become a problem. On the other hand, in the case of gallium phosphide (GaP) green light emitting devices, N layer and P layer are grown from one solution rather than growing from separate solutions.
It is known that a light-emitting element based on the so-called impurity compensation method in which the P layer and the P layer are continuously grown has superior light emission characteristics.

The first invention was made in view of the above facts,
P with simultaneous addition of zinc (Zn) and tellurium (Te)
After growing a P-type layer from a type growth solution,
After Zn is removed by vacuum treatment and aluminum is added, an N-type layer is successively grown from the same solution, resulting in stable characteristics by preventing various defects from being introduced near the P-N interface.
A method for manufacturing a GaAlAs layer light emitting device is provided.

However, even in this case, since the solution is separated by sliding after growing the N-type layer, there are problems such as scratches on the wafer surface due to the inclusion of polycrystals and surface defects due to the solution remaining on the wafer surface. becomes. In addition to the above-mentioned problems, the horizontal slide boat method also has the following problems.

In the case of liquid phase epitaxial growth of GaAlAs,
Since aluminum, which is very easily oxidized, is added to the solution, oxygen in the solution and oxygen adsorbed on the growth jig etc. must be sufficiently removed by sufficient dry baking before growth. However, in the Slight Boat method, since the solution and the substrate crystal are always in the same temperature zone, if the solution baking time is too long, the problem of thermal deterioration of the substrate crystal arises. Therefore, the baking time cannot be selected independently from the viewpoint of oxygen removal.

When a large number of substrate crystals are charged by the slide boat method, the structure becomes complicated and the operability is poor, which is problematic as a mass production method.

Therefore, the second invention of the present invention has been made in view of the above facts. As a result of various studies, the present inventors have succeeded in providing a method for mass-producing GaAlAs light emitting devices that solves the above-mentioned problems by employing a vertical immersion method.

Examples will be described below with reference to the figures.

Example 1 FIG. 2 schematically shows a graphite slite boat used in the implementation of the first invention.
A P-type GaAs substrate 3 is installed on the lower slider 1, and the growth solution 4 contains 50 g of metallic gallium, 4 g of GaAs polycrystal, 80 mg of aluminum (Al), 50 mg of zinc,
The composition contains 2mg of tellurium. Moreover, 300 mg of Al9 is installed in the upper slider 8.

Place the slider in this state in the soaking zone of an electric furnace, perform vacuum replacement, and heat to 900℃ while flowing hydrogen gas.
Increase the temperature to. After holding the temperature at 900°C for 1 hour, the slider 1 is moved to bring the substrate 4 into contact with the growth solution 4, which is then cooled to 860°C at a cooling rate of 0.5°C/min to grow a P-type layer. Growth is suspended at this temperature,
The solution is maintained under a reduced pressure of about 2 Torr for about 2 hours while flowing Ar gas to remove Zn from the solution. Next, the pressure is returned to normal and hydrogen gas is supplied again, and the upper slider 3 is moved to add Al9 to the solution. Approximately 10 minutes after addition, the temperature is raised again by 10°C. After holding at 870℃ for about 10 minutes, slowly cool it again to 830℃ at a cooling rate of 0.5℃/min.
When the N-type layer grows and reaches 830℃, slider 1
and separate the growth solution. Through this step, a P-type layer of about 20 μm and an N-type layer of about 20 μm were grown. As a result of compositional analysis by EPMA, the P-type layer was Ga _0.66 Al _0.34 As, and the N layer was Ga _0.42 Al _0.58 As. The light emission wavelength of the obtained light emitting device was 6650 Å, and the light emission output was about 1.5 times that of the case where the P type layer and the N type layer were grown from separate solutions.

In the above example, the decompression treatment time was set to 2 hours, but 1
If the time is longer than 2 hours, the N-type layer may not be obtained due to insufficient removal of Zn, but if the time is 2 hours or more, an N-type layer can be obtained with good reproducibility.

Example 2 FIG. 3 schematically shows an apparatus for the vertical dipping method used in the implementation of the second invention. It is composed of an electric furnace 11 and a quartz reaction tube 12. Inside the furnace, 3 kg of metallic gallium, 240 g of GaAs polycrystal,
A substrate holder 13 on which a P-type GaAs substrate 3 is mounted is installed at the top of the reaction tube outside the furnace where a growth solution 4 containing 120 mg of tellurium is mixed. Furthermore, a Zn charger 6 and an Al charger 7 are installed at the top of the reaction tube. In this state, after vacuum replacement, the temperature is raised to 900°C while flowing hydrogen gas. After holding at 900° C. for 2.5 hours, 3 g of Zn was added from the Zn charger 6 and 4.8 g of Al was added from the Al charger 7. After holding the temperature at 900° C. for another 30 minutes, the substrate holder 13 is preheated directly above the growth solution, then immersed in the growth solution, and slowly cooled to 860° C. at a cooling rate of 0.5° C./min to grow a P-type layer. At this temperature, growth is temporarily stopped and while Ar gas is flowing, approximately
After holding the solution under a reduced pressure of 2 Torr for 2 hours to remove Zn from the solution, the pressure is returned to normal pressure, hydrogen gas is flowed again, and 18 g of Al is added from the Al injector 7. After 30 minutes after the addition, the temperature was raised by 10°C, held at 870°C for 10 minutes, and slowly cooled again to 830°C at a cooling rate of 0.5°C/min to grow the N layer. When the temperature reached 830°C, the substrate holder 13 was It is separated from the growth solution and pulled up to the top of the reaction tube. This process resulted in the growth of a P-type layer of approximately 25 μm and an N-type layer of approximately 25 μm. Also, the results of composition analysis by EPMA show that the P-type layer is Ga _0.68 Al _0.32 As, and the N-type layer is Ga _0.38 Al _0.62 As.
It was hot. The emission wavelength of the obtained light emitting device is 6700
Å, the luminous output was almost the same as that of Example 1.

In Example 1, surface defects were observed on the surface of the N-type layer due to scratches caused by the slider and residual solution, but in Example 2, an almost perfect mirror surface was obtained.

By successively growing a P-type layer and an N-type layer from the same solution, it is possible to manufacture a GaAlAs light-emitting device with stable characteristics, and the gallium consumption rate has also been reduced to about half that of the conventional method. In addition, by adopting the vertical dipping method and using a substrate holder with a structure in which many sheets are bundled,
It has become possible to process 30 wafers with a diameter of approximately 50 mmφ in one growth, and it has become possible to obtain almost perfect mirror surfaces.

In the above embodiment, red light was emitted with a wavelength of 6,600 to 6,700 Å, but by changing the composition of aluminum in the P-type GaAlAs layer, it is possible to emit light with a wavelength of 6,500 to 9,000 Å. In addition, tellurium (Te) is used as an N-type additive.
was used, but sulfur (S), selenium (Se) may also be used, and the P-type additive may be cadmium (Cd).

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional horizontal slide boat. 1...Lower slider, 2...Upper slider, 3
...P-type GaAs substrate, 4...P-type growth solution, 5...N-type growth solution. FIG. 2 is a diagram showing an example of a horizontal slide boat used in the present invention. 1...Lower slider, 2...Middle slider, 3
...P-type GaAs substrate, 4...Growth solution, 8...Upper slider, 9...Additional aluminum. FIG. 3 is a diagram showing an example of an apparatus for the vertical dipping method used in the present invention. 3... P-type GaAs substrate, 4... Growth solution, 6... Zn charger, 7... Al charger, 11... Electric furnace, 12... Quartz reaction tube, 13... Substrate holder.

Claims (1)

[Claims] 1. GaAlAs having a P-type GaAlAs layer and an N-type GaAlAs layer on the P-type gallium arsenide substrate.
When manufacturing a light emitting device by liquid phase epitaxial growth, a P-type GaAlAs layer is first grown from an aluminum (Al)-gallium (Ga) solution containing zinc (Zn) and tellurium (Te), and then the solution is grown by vacuum treatment. A method for manufacturing a GaAlAs light emitting device, which comprises removing Zn therein, adding Al, and then successively growing an N-type GaAlAs layer from the same solution. 2. Claim 1, characterized in that a vertical dipping method is used during liquid phase epitaxial growth.
A method for manufacturing a GaAlAs light emitting device as described in .