JPH0728079B2 - Method for manufacturing semiconductor laser - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor laser.

[Prior Art and its Problems] Conventional vapor phase epitaxy techniques for obtaining semiconductor thin film crystals include metal organic chemical vapor deposition (MO-CVD) and molecular beam epitaxy (MBE). Atomic layer epitaxy method (hereinafter referred to as ALE method) and the like are known. However, MO-CVD method
Since the Group II and V elements are simultaneously introduced into the reaction chamber using hydrogen gas as a carrier and are grown by thermal decomposition, the quality of the growth layer is poor. Further, there are drawbacks such that it is difficult to control the order of monomolecular layer. In addition, a growth temperature of 600 ° C. or higher is usually used to improve the crystal quality.

On the other hand, the MBE method, which is well known as a crystal growth method using ultra-high vacuum, is inferior to the vapor phase growth method using a chemical reaction because the physical adsorption is the first step. When growing a III-V compound semiconductor such as GaAs, III
Group and V group elements are used as sources, and the source source itself is installed in the growth chamber. Therefore, it is difficult to control the emission gas and evaporation amount obtained by heating the source source, and to replenish the source, and it is difficult to keep the growth rate constant for a long time. Further, the vacuum device such as evacuation of the evaporated material becomes complicated. Furthermore, it is difficult to precisely control the stoichiometric composition (stoichiometry) of the compound semiconductor, and as a result, high quality crystals cannot be obtained. Also, in order to form a mixed crystal, good crystals cannot be obtained unless the temperature is about 600 ° C. or higher with GaAlAs, and it can be said that the heterojunction interface with GaAs has unevenness of 1 to several atomic layers and is good. There is no such thing.

For the ALE method, T. Suntola et al., USP No. 4058430 (1977).
As described in (1), a semiconductor element is supplied in a pulsed form and deposited on a substrate to grow a crystal atomic layer by atomic layer, but a semiconductor single crystal cannot be grown. That is, in order to form a single crystal thin film,
The method used by M. Pessa et al. In the same group is not the ALE method but the collection of papers of the American Vacuum Society in 1984 (J. Vac. Sci.
l, A2 (1984) 418), which is based on the MBE method.

Thus, the MO-CVD method and MBE method cannot obtain high-quality crystals satisfying the stoichiometric composition at low temperature, and it is difficult to form monolayers, while the ALE method does not There was a drawback that crystals could not be obtained.

[Object of the Invention] The present invention eliminates the above-mentioned drawbacks of the prior art, improves the quality of the crystal growth layer by controlling the stoichiometric composition, and heats the substrate in a lower temperature region and achieves the accuracy of a single molecular weight. It is an object of the present invention to provide a method for manufacturing a semiconductor laser having a high quality heterojunction by forming a growth film.

[Summary of the Invention] Therefore, according to the present invention, (1) a gas containing component elements of Ga, As, Al, and P and a gas containing component elements to be impurities are introduced from the outside into a growth tank evacuated to vacuum. And a means for heating the n ^{+ -type} GaAs substrate, and a light source for irradiating the n ^{+ -type} substrate with a light source, and the inside of the growth tank is evacuated to 10 ⁻⁷ to 10 ⁻⁹ Pa. In addition, while heating the n ^{+ -type} substrate to about 300 ~ 600 ℃, while irradiating the n ^{+ -type} substrate with light from the light source, the gas containing Ga or the gas containing Al at the same time as the pressure in the growth tank is increased. 0.5 to 1 in the range of 10 ^-1 to 10 ^-7 Pa
It was introduced for 0 seconds, then the gas in the growth tank was exhausted,
Gas containing Al or gas containing Al at the same time
By repeating the operation of introducing for 2 to 200 seconds within the range of 10 ^-1 to 10 ^-7 Pa, the n _- type Ga _1- xAlx is formed on the n ^{+ -type} substrate.
Step of growing As or Ga _1- xAlxAs _1- yPy one by one molecular layer, step of forming undoped GaAs thereon, and further growing p _- type Ga _1- xAlxAs or Ga _1- xAlxAs _1- yPy step of, after forming an insulating film thereon, forming a p ⁺ -type layer by performing impurity diffusion by Zn to the p-type layer to form an opening in a predetermined position, the alloy into the p ⁺ -type layer To form a p ^{+ -type} electrode and a step of depositing an alloy on the n ^{+ -type} substrate to form an n ^{+ -type} electrode, thereby sequentially manufacturing a semiconductor laser.

The present invention also provides (2) means for introducing a gas containing each component element of Ga, As, Al, and P and a gas containing a component element that becomes an impurity from the outside into a growth tank evacuated to a vacuum.
Using a crystal growth apparatus equipped with a means for heating an n ^{+ -type} GaAs substrate and a light source for irradiating the n ^{+ -type} substrate with light, the inside of the growth tank is evacuated to 10 ^-7 to 10 ^-9 Pa, and About n ^{+ type} substrate
While heating to 300 to 600 ° C. and irradiating the n ^{+ -type} substrate with light from the light source, a gas containing Ga or a gas containing Al at the same time has a pressure in the growth tank of 10 ⁻¹ to 10 ⁻⁷ Pa. After introducing the gas in the range for 0.5 to 10 seconds, and then exhausting the gas in the growth tank, the gas containing As or the gas containing Al at the same time has a pressure in the growth tank of 10 ^-1.
10-7 By repeating the operation of introducing 2-200 seconds within an amount of Pa, the n ⁺ -type substrate to the n-type Ga _1-x Alx As or
A step of growing Ga _1- xAlxAs _1- yPy one molecular layer at a time, and a step of repeatedly growing an undoped Ga _1- xAlxAs _1- yPy layer and a GaAs layer thereon to form a hetero layer Forming a p ^{+ -type} Ga _1- xAlxAs or Ga _1- xAlxAs _{1 -} yPy on the hetero layer and then forming a p ^{+ -type} GaAs layer thereon, insulating on the p ^{+ -type} GaAs layer After forming the film, a step of forming an opening at a predetermined place, a step of depositing an alloy from the opening to the p ^{+ -type} layer to form a p ^{+ -type} electrode, and an alloy is vapor-deposited on the n ^{+ -type} substrate. The step of forming an n ^{+ -type} electrode is sequentially performed to manufacture a semiconductor laser having a quantum well structure.

[Examples of the Invention] In the following, examples of the present invention are used as semiconductors for GaAs and Ga _1- x AlxAs.
Alternatively, a case of using Ga _1- xAlxAs _1- yPy will be described as an example.

FIG. 1 is a block diagram of a semiconductor laser manufacturing apparatus according to an embodiment of the present invention, in which 1 is a growth tank and the material is a metal such as stainless steel, 2 is a gate valve, 3 is an ultrahigh growth tank 1. An evacuation device for evacuation to a vacuum, 4 a nozzle for introducing a gas containing Ga such as TMG (trimethylgallium), and 5 an AsH ₃
Nozzle for introducing, 6 is a nozzle for introducing a gas containing Al such as TMA (trimethylaluminum), 7 is a nozzle for introducing a gas containing P such as PH ₃ , 8 is GaAs and Ga _1- xAlxAs
A nozzle for introducing a gas containing S such as H ₂ S which becomes an n-type impurity into _1- yPy, and 9 becomes a p-type impurity like the nozzle 8.
Nozzles for introducing a gas containing Zn such as TMZ (trimethylzinc), 10,11,12,13,14,15 are valves for opening and closing the nozzles, and gas sources 16 (Ga (CH ₃ ) ₃ etc.), 17 ( AsH ₃ ), 18 (TM
A), 19 (PH ₃ etc.), 20 (TMZ etc.), 21 (H ₂ S etc.). Reference numeral 22 is a heater for heating the substrate, which is a W (tungsten) wire enclosed in quartz glass, and the wiring is not shown. 23 is a thermocouple for temperature measurement. 24 is a light source for irradiating the substrate with light, and a mercury lamp, an excimer laser, an argon ion laser, or the like can be used. 25 is a window for light irradiation,
26 is a pressure gauge for measuring the pressure in the growth tank, 27 is GaAs
The substrate.

With this structure, the growth of GaAs is carried out by first opening the gate valve 2 and using the ultrahigh vacuum exhaust device 3 to grow the inside of the growth tank 1 to 10 ^-7 to 10 ^-8.
Exhaust to about pascal (abbreviated as Pa below). Next, GaAs
After heating the substrate 27 to, for example, 300 to 600 ° C. by the heater 22, TMG is introduced by opening the valve 8 for 0.5 to 10 seconds within the range where the pressure in the growth tank 1 is 10 ⁻¹ to 10 ⁻⁷ Pa. Next, after the TMG is evacuated from the growth tank 1, AsH ₃ 13 is valved for 2 to 200 seconds within a range where the pressure in the growth tank 1 is 10 ^-1 to 10 ^-7 Pa.
Open and install. Thereby, one molecular layer can be grown.

On the other hand, in the growth of Ga _1- xAlxAs _1- yPy, one molecular layer can be grown by introducing Ga and Al of the group III and then introducing As and P of the group V like the growth of GaAs.

The impurities can be added by introducing a gas containing a group II at the same time as Ga in the p-type and a gas containing a group VI at the same time in the n-type as As, respectively.

Here, Ga _1- xA as a heterojunction of the laser diode
Since the composition of lxAs _1- yPy compensates the lattice constant with GaAs, y may be set to about 0.01 when x = 0.3, or Ga _1- xAlxAs containing no P may be used in some cases.

Further, the heating of the substrate has been described as the heating by the heater 22. However, an infrared lamp heating source may be provided outside the growth tank 1. Furthermore, at the same time as heating the substrate, Hg
The growth layer may be irradiated with light from the lamp 24. In such a case, since the growth temperature can be lowered to about 400 ° C., it becomes possible to control auto-doping of impurities or mutual diffusion.

As described above, the gases containing the III-V group or the mixed crystal component elements thereof are alternately introduced, and the crystal growth is advanced by the chemical reaction to complete the stoichiometric composition. The crystal growth layer of the mixed crystal can be grown for each molecular layer, and a high quality semiconductor laser which cannot be obtained by the conventional method can be manufactured.

FIG. 2 shows the manufacturing process of the semiconductor laser produced using the apparatus described above Figure 1, 30 in FIG. (A) is n ⁺ ([rho
= 1 × 10 ⁻³ Ω · cm) GaAs substrate. An n-type (n = 1 × 10 ¹⁸ cm ⁻³ ) Ga _1- xAlxAs _1- yPy layer 31 is heteroepitaxially grown on this substrate 30 (b). Then, an andrope n-type GaAs layer 32 is grown thereon (c).
Further thereon, a p _- type Ga _1- xAlxAs _1- yPy layer 33 is grown (d). The thickness of the growth layer at this time is Ga _1- xAlxAs _1- yPy
Layers 31 and 33 are 0.5 μm, and n-type GaAs layer 32 is 500
Form ~ 1000Å. An insulating film 34 such as SiO ₂ or Si ₃ N ₄ is formed on the entire surface of the p layer of this double-heterostructure semiconductor, and then an opening is provided (e). Next, impurities are diffused into the exposed p-type Ga _1- xAlxAs _1- yPy layer 32 by Zn to form ap ⁺ layer 35 (f). Au-Zn to the p ⁺ layer 35,
An alloy such as Ag-Zn is deposited to form the p ⁺ electrode 36 (g).
Next, the n ⁺ substrate 30 is thinned to about 100 μm, and An-Ge, A
An n ⁺ electrode 37 is formed from a u-Ge-Ni alloy (h). The laser diode can be manufactured by opening the thus-formed wafer to a size of about 100 μm × 200 μm and packaging it by bonding or the like.

Although the manufacture of the simplest double-hetero laser diode has been described above, it goes without saying that other structures can be realized by the crystal growth method.

FIG. 3 shows another embodiment of the present invention, showing a manufacturing process of a so-called quantum well type semiconductor laser. 40
Is a n ⁺ (ρ = 1 × 10 ⁻³ Ω · cm) GaAs substrate (a).
On this substrate 40, n (n = 1 × 10 ¹⁸ cm ^-3 ) type Ga _1- xAlxAs _1-
A yPy layer 41 of 0.5 μm is epitaxially grown using the apparatus shown in FIG. 1 (b). Undoped Ga _1- x Alx
An As _1- yPy layer 42 is formed (c), and a GaAs layer 43 is further grown thereon (d). The thickness of these growth layers 42,43 is about 100.
Repeat with Å to grow repeatedly (e). Furthermore,
The growth layers 42 and 43 are repeatedly grown to form 10 hetero layers 45 (f). Furthermore, p ⁺ (p
= 1 × 10 ¹⁸ cm ^-3 ) type Ga _1- xAlxAs _1- yPy layer 46 is formed, and a p ⁺ (p = 1 × 10 ¹⁹ cm ^-3 ) type GaAs layer 47 is formed thereon (g). An SiO ₂ or Si ₃ N ₄ film 48 is attached and opened on the p ^{+ -type} GaAs layer 47 of the wafer thus grown by the molecular layer epitaxial growth method (h), and the p ⁺ layer 47 is Au.
Ohmic contacts 49, 50 are formed on the n ⁺ substrate 40 such as -Zn, Ag-Zn or the like by an alloy such as Au-Ge or Au-Ge-Ni (i). Thereby, a quantum well type semiconductor laser can be manufactured.

[Effects of the Invention] As described above, according to the present invention, a high-quality crystal thin film satisfying a stoichiometric composition can be grown with the accuracy of a monolayer, and a high-quality GaAs type having a double hetero structure can be obtained. Laser diode can be manufactured.

[Brief description of drawings]

FIG. 1 is a block diagram of a crystal growth apparatus according to an embodiment of the present invention, and FIGS. 2 and 3 are explanatory views of a manufacturing process of a semiconductor laser manufactured by the apparatus of FIG. ) ~
(H) is a manufacturing process explanatory view of a double hetero type semiconductor laser, and FIGS. 3 (a) to (i) are manufacturing process explanatory views of a quantum well type semiconductor laser. 1 ... metal, 2 ... gate valve, 3 ... exhaust device, 4,
5,6,7,8,9 …… Nozzle, 10-15 …… Valve, 16-21 ……
Gas source, 22 ... Heater, 23 ... Thermocouple, 24 ... Light source,
25 ... windows.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaoru Motoya 2-9-9 Yonegabukuro, Sendai City, Miyagi 406 (56) References Applied Physics 53 [6], 1984-6, pp. 516-P. 520 “Compound semiconductor devices [▲ I ▼]” (Industry Research Institute of the Stock Company, published on July 15, 1987) P.126 to P.131

Claims (2)

[Claims] 1. A growth chamber evacuated to a vacuum is supplied with Ga and A from the outside.
a means for introducing a gas containing each elemental element of s, Al, and P and a gas containing an elemental element that becomes an impurity, and n ^{+ -type} Ga
Using a crystal growth apparatus equipped with a means for heating the As substrate and a light source for irradiating the n ^{+ -type} substrate with light, the inside of the growth tank is evacuated to 10 ^-7 to 10 ^-9 Pa, and the n ⁺
While heating the shaped substrate to about 300 to 600 ° C. and irradiating the n ^{+ type} substrate with light from the light source, a gas containing Ga or at the same time a gas containing Al is grown at a pressure of 10 ⁻¹ to 10 ^{− In the} range of ⁷ Pa
After introducing the gas for 0.5 to 10 seconds and then exhausting the gas in the growth tank, a gas containing As or a gas containing Al at the same time is 2 to 200 in the range where the pressure in the growth tank is 10 ^-1 to 10 ^-7 Pa. By repeating the operation of introducing for a second, n-type Ga is formed on the n ^{+ -type} substrate.
Step of growing _{1 -} xAlxAs or Ga _1- xAlxAs _1- yPy for each molecular layer, step of forming undoped GaAs thereon, and p _- type Ga _{1 -} xAlxAs or Ga _1- xAlxAs _1- yPy
A step of growing a p ^{+ -type} layer by forming an opening at a predetermined location and diffusing impurities into the p-type layer by Zn to form a p ^{+ -type} layer after forming an insulating film on the p ^{+ -type} layer. A semiconductor laser is manufactured by sequentially performing a step of vapor-depositing an alloy to form ap ^{+ -type} electrode, and a step of vapor-depositing an alloy onto the n ^{+ -type} substrate to form an n ^{+ -type} electrode. Manufacturing method of semiconductor laser. 2. Ga, A from the outside in a growth tank evacuated to a vacuum
a means for introducing a gas containing each elemental element of s, Al, and P and a gas containing an elemental element that becomes an impurity, and n ^{+ -type} Ga
Using a crystal growth apparatus equipped with a means for heating the As substrate and a light source for irradiating the n ^{+ -type} substrate with light, the inside of the growth tank is evacuated to 10 ^-7 to 10 ^-9 Pa, and the n ⁺
While heating the shaped substrate to about 300 to 600 ° C. and irradiating the n ^{+ type} substrate with light from the light source, a gas containing Ga or at the same time a gas containing Al is grown at a pressure of 10 ⁻¹ to 10 ^{− In the} range of ⁷ Pa
After introducing the gas for 0.5 to 10 seconds and then exhausting the gas in the growth tank, a gas containing As or a gas containing Al at the same time is 2 to 200 in the range where the pressure in the growth tank is 10 ^-1 to 10 ^-7 Pa. By repeating the operation of introducing for a second, n-type Ga is formed on the n ^{+ -type} substrate.
A step of growing _{1 -} xAlxAs or Ga _1- xAlxAs _1- yPy by one molecular layer, a hetero layer by repeatedly growing an undoped Ga _1- xAlxAs _1- yPy layer and a GaAs layer thereon. Forming a p ⁺ -type Ga _{1 -} xAlxAs or Ga _1- xAlxAs _1- yP on the hetero layer.
After forming y, a step of forming ap ^{+ -type} GaAs layer thereon, a step of forming an insulating film on the p ^{+ -type} GaAs layer, and then forming an opening at a predetermined location, A semiconductor laser having a quantum well structure by sequentially performing a step of depositing an alloy on a ^{+ type} layer to form ap ^{+ type} electrode, a step of depositing an alloy on the n ^{+ type} substrate to form an n ^{+ type} electrode. A method of manufacturing a semiconductor laser, comprising: