JPH07249823A - Manufacture of semiconductor light-emitting device - Google Patents

Abstract

PURPOSE:To improve the manufacturing method of a semiconductor laser which emits a ray of visible light, in more detail, in a blue-green region. CONSTITUTION:The manufacture is provided with a process wherein, after a compound semiconductor layer containing Zn has been formed, the surface layer of the compound semiconductor layer which has been heat-treated at a temperature of T and for a time of (t) is etched at a thickness of (d)=[D0 exp{-Q/(kT)}Xt]<1/2> [where D0 represents the diffusion coefficient of holes of Zn, Q represents the activation energy of the holes of Zn and (k) represents the Boltzmann constant] or higher and with a process wherein a metal electrode is formed on the etched surface of the compound semiconductor layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor light emitting device, and more particularly, to improvement of a method of manufacturing a semiconductor laser that emits visible light in the blue-green region.

[0002]

2. Description of the Related Art A conventional method for manufacturing a semiconductor light emitting device will be described below. A semiconductor light emitting device according to a conventional example is a visible light semiconductor laser that is composed of a II-VI group compound and emits light in a blue-green region.
It is a semiconductor laser containing a compound of the system.

First, as shown in FIG. 4 (a), MBE
P ⁺ -GaAs substrate 1 using (molecular beam epitaxy) method
A p-ZnS _0.06 Se _0.94 clad layer 2, a Cd _0.2 Zn _0.8 Se active layer 3 and an n-ZnS _0.06 Se _0.94 clad layer 4 are sequentially epitaxially grown thereon. Next, as shown in FIG. 4 (b), a SiO ₂ film 5 is deposited on the n-ZnS _0.06 Se _0.94 cladding layer 4 by using the plasma CVD method, and a part thereof is selectively removed in stripes by wet etching. By doing so, the opening 5A is formed and a current constriction structure is created. Note that SiO ₂
The step of depositing the film 5 is performed at a temperature of about 300 ° C. in order to make the SiO ₂ film 5 dense in order to prevent entry of moisture and the like.

By the heat treatment at this time, n-ZnS _0.06 Se
_0.94 compensation defect diffusion cause of Zn vacancies of the surface of the cladding layer 4 is formed, the high-resistance layer (not shown) on the surface layer of the n-ZnS _0.06 Se _0.94 cladding layer 4 is formed. Then, FIG. 4 (c)
N-ZnS _0.06 Se _0.94 exposed through the opening 5A as shown in FIG.
The surface of the clad layer 4 was lightly wet-etched with a potassium chromium oxide (KCrO) -based etching solution to produce n-ZnS _0.06.
The high resistance layer (not shown) on the surface of the Se _0.94 clad layer 4 is removed.

After that, an In electrode 6 was formed on the surface of the n-ZnS _0.06 Se _0.94 cladding layer 4 exposed from the upper portion of the SiO ₂ film 5 and the opening 5A by using a vacuum evaporation method, and the p ⁺ -GaAs substrate 1 was also formed. AuZn electrodes 7 are vapor-deposited on the back surface of each of them as shown in FIG. 5, and a semiconductor laser is completed through the following ordinary laser manufacturing process.

[0006]

[Problems to be Solved by the Invention]
According to the conventional method for manufacturing a semiconductor light emitting device, n-ZnS_0.06Se
_0.94The high resistance layer formed on the surface of the clad layer 4 is a post-process.
SiO₂The film thickness changes under the influence of the heat treatment conditions of the film 5.
Therefore, the high resistance layer is completely removed by wet etching.
There was something I couldn't do.

Then, the resistance value of the In electrode 6 which is an ohmic electrode is very large depending on the resistance value of the surface of the n-ZnS _0.06 Se _0.94 clad layer 4, and therefore n-ZnS _0.06 is obtained even in one atomic layer. If a high resistance layer is present on the surface of the Se _0.94 cladding layer 4, good ohmic contact cannot be obtained. On the contrary, if the wet etching time is set too long in order to completely remove the high resistance layer, the thickness of the cladding layer 4 becomes thin, light leaks out and cannot be confined, and good laser emission cannot be achieved. There was a problem.

If good ohmic contact cannot be established in this way, there arises a problem that various problems such as increase in operating current of the semiconductor laser, increase in heat generation, and decrease in device life are caused. The present invention has been made in view of the above circumstances, and based on the temperature and time of heat treatment during deposition of a SiO ₂ film, a high resistance layer formed on the surface of the clad layer that makes ohmic contact is formed. An object of the present invention is to provide a method for manufacturing a semiconductor light emitting device that can be reliably removed without affecting laser light emission.

[0009]

The above-mentioned problems are solved by forming a compound semiconductor layer containing Zn at a temperature T and a time t.
The surface layer of the compound semiconductor layer that has undergone the heat treatment of d = [D
₀ exp {−Q / (kT)} × t] ^1/2 (D ₀ is the diffusion coefficient of Zn vacancy, Q is the activation energy of Zn vacancy,
k is a Boltzmann constant) and has a thickness of d or more, and a step of etching the surface of the compound semiconductor layer, and a step of forming a metal electrode on the etched surface of the compound semiconductor layer. It is solved by the manufacturing method.

[0010]

[Operation] In a conventional method for manufacturing a semiconductor light emitting device,
Since the high resistance layer could not be completely removed, n-ZnS was formed by using the plasma CVD method at the temperature T.
Depositing a SiO ₂ film 5 on _{0. 06} Se _0.94 cladding layer 4, after forming the opening 5A, n-ZnS _0.06 Se _0.94 cladding layer 4
An experiment was carried out to confirm the relationship between the temperature T and the thickness of the high resistance layer formed above.

The graph of FIG. 1 shows the relationship between the heat treatment temperature and the thickness of the high resistance layer when the heat treatment time in the step of depositing the SiO ₂ film 5 is kept constant at 1000 seconds. As shown in FIG. 3, the thickness of the high resistance layer greatly changes depending on the temperature of the heat treatment, and (thickness of the high resistance layer) = [D ₀ exp {−Q / (kT)}.
Xt] ^1/2 (D ₀ is the diffusion coefficient of Zn vacancies, Q is the activation energy of Zn vacancies, and k is the Boltzmann constant), Z
It was confirmed that the solution can be approximated by the solution of the diffusion equation of n holes.

Therefore, in the present invention, after the compound semiconductor layer containing Zn is formed, heat treatment is performed at a temperature T for a time t so that the surface layer of the compound semiconductor layer is d = [D ₀ exp {-Q.
/ (KT)} × t] ^1/2 (D ₀ is the diffusion coefficient of Zn vacancies, Q is the activation energy of Zn vacancies, and k is the Boltzmann constant). By etching, a metal electrode is formed on the compound semiconductor layer,
As an example thereof, as shown in FIG. 2, a passivation film 15 is formed on the second cladding layer 14 by a heat treatment process at a temperature T for a time t, and an opening 15A is formed to expose the second cladding layer 14. After that, using the passivation film 15 as a mask, d = [D ₀ exp (−Q / kT) × t] ^1/2 (D ₀ is a diffusion coefficient of Zn vacancy, Q is activation of Zn vacancy) Energy, k is Boltzmann's constant), a thickness d, that is, the surface of the second cladding layer 14 is etched by not less than the diffusion depth of Zn vacancies obtained by the diffusion equation.

Therefore, by etching the surface of the second clad layer 14 having a thickness not less than the above d, the high resistance layer formed on the surface layer of the second clad layer 14 by heat treatment can be surely removed. It will be possible. This makes it possible to suppress various problems caused by the high resistance layer formed on the surface of the second cladding layer 14 such as an increase in operating current, an increase in heat generation, and a decrease in device life as much as possible.

[0014]

EXAMPLE A method for manufacturing a semiconductor light emitting device according to an example of the present invention will be described below. A semiconductor light emitting device according to an embodiment of the present invention is a Fabry-Perot type visible light semiconductor laser that is composed of a II-VI group compound and emits light in a blue-green region, and specifically, a ZnSe-based compound. It is a semiconductor laser including.

First, as shown in FIG. 2A, MBE
(Molecular beam epitaxy) method is used, and the substrate temperature is 250 ° C.
Under the above conditions, a p-ZnS _0.06 Se _0.94 clad layer 12 having a film thickness of 2 μm and a film thickness of 1 is formed on the Zn-added p ⁺ -GaAs substrate 11.
00Å Cd _0.2 Zn _0.8 Se active layer 13 and 2 μm thick n
-ZnS _0.06 Se _{0.94 The} cladding layer 14 is sequentially epitaxially grown.

Next, as shown in FIG. 2B, a SiO ₂ film 15 having a film thickness of 500 Å is deposited on the n-ZnS _0.06 Se _0.94 cladding layer 14 by using a plasma CVD method, and a hydrofluoric acid-based etching is performed. By selectively removing a part thereof in a stripe shape by wet etching using a liquid, an opening 15A is formed and a current constriction structure is created. In the step of depositing the SiO ₂ film 15, the SiO ₂ film 1 is used for the purpose of preventing the intrusion of moisture and the like.
In order to make 5 dense, at a substrate temperature of about 300 ° C., 3
Do about 0 minutes.

During this heat treatment, compensation defects are formed due to the diffusion of Zn vacancies on the surface of the n-ZnS _0.06 Se _0.94 cladding layer 14, and a high resistance layer is formed on the surface layer. Corresponding to the diffusion depth of Zn vacancies obtained by the diffusion equation, d = [D ₀ exp {-Q / (kT)} × t] ^1/2 (D ₀ is the diffusion coefficient of Zn vacancies) , Q is the activation energy of Zn vacancies, and k is the Boltzmann constant)
It can be approximated that a high resistance layer is formed on the surface layer of the n-ZnS _0.06 Se _0.94 cladding layer 14.

Specifically, the actual numerical value, that is, D ₀ = 3.13 × 10 ⁹ (m ² / s) k = 1.38 × 10 ^-23 (J / K) Q = 2 × 10 ^-19 ( J) Substituting t = 30 × 60 = 1800 (s) T = 273 + 300 = 573 (K), it is said that a high resistance layer of d = 8 × 10 ⁻⁹ (m) = 8 (nm) is formed. Conceivable.

Next, as shown in FIG. 2C, n is exposed from the opening 15A in order to remove the above-mentioned high resistance layer.
-ZnS _0.06 Se _0.94 The surface of the clad layer 14 is wet-etched with a chromium oxide potassium (KCrO) -based etching solution for about 10 nm. As described above, the thickness of the high resistance layer formed on the surface layer of the n-ZnS _0.06 Se _0.94 cladding layer 14 is
Since the thickness is 8 (nm), it is possible to completely remove the high resistance layer by etching the surface layer by about 10 nm.

After that, as shown in FIG. 3A, In is deposited on the surface of the n-ZnS _0.06 Se _0.94 cladding layer 14 exposed from the upper portion of the SiO ₂ film 15 and the opening 15A by using a vacuum deposition method.
The electrode 16 and the AuZn electrode 17 are vapor-deposited on the back surface of the p ⁺ -GaAs substrate 1, respectively, and cleaved to form opposite cleaved surfaces according to the usual Fabry-Perot laser manufacturing process, and the cleaved surfaces are respectively formed on the cleaved surfaces. By forming a high-reflection film 18 and a low-reflection film 19 made of a multi-layered SiO ₂ film or Si, a semiconductor laser as shown in FIG. 3B is completed.

When the semiconductor laser having the above structure was operated, good ohmic contact was obtained, and no light bleeds in the clad layer, and good emission characteristics were obtained. As described above, according to the method for manufacturing the semiconductor light emitting device according to the embodiment of the present invention, the SiO ₂ film 15 is formed on the n-ZnS _0.06 Se _0.94 cladding layer 14 by the heat treatment process at the temperature T and the time t. , Openings 15A are formed to form n-ZnS _0.06 Se _0.94
After exposing the cladding layer 14, using the SiO ₂ film 15 as a mask, d = [D ₀ exp (−Q / kT) × t] ^1/2 (D ₀ is the diffusion coefficient of Zn, and Q is the activity of Zn. The energy d, k is the Boltzmann constant), that is, the thickness d, that is, the surface of the n-ZnS _0.06 Se _0.94 clad layer 14 is etched only by the diffusion of Zn. Specifically, d = 8 nm, and The surface of the second cladding layer 13 is etched by 10 nm.

For this reason, the above thickness d or more n-ZnS _0.06 S
By etching the surface of the e _0.94 clad layer 14, the surface high resistance layer can be completely removed. This increases the operating current of the semiconductor light emitting device completed through this step caused by the high resistance layer,
Various problems such as increased heat generation and shortened device life can be suppressed as much as possible.

Although the present embodiment describes the case where ZnSSe is used for the cladding layer, the present invention is not limited to this, and other materials such as ZnMgSSe and ZnMnSSe.
Even when it is applied to a semiconductor laser diode in which a material containing is used as a cladding layer, the same effect is obtained. In this case, there is room for using not only the diffusion coefficient and activation energy of Zn but also the diffusion coefficient and activation energy of Se.

Further, although the Fabry-Perot type semiconductor laser has been described in the present embodiment, the present invention is not limited to this, and a structure in which a compound semiconductor containing either Zn or Se is heat-treated and then contact is made with a metal electrode. As long as it is a semiconductor light emitting device having any of the above, substantially the same effects can be obtained with any semiconductor light emitting device.

[0025]

As described above, according to the present invention, Zn
After forming the compound semiconductor layer containing s, the surface of the compound semiconductor layer is subjected to heat treatment at a temperature T for a time t, and d = [D ₀
exp {−Q / (kT)} × t] ^1/2 (D ₀ is the diffusion coefficient of Zn vacancy, Q is the activation energy of Zn vacancy, k
Is the Boltzmann constant) and the surface of the compound semiconductor layer having a thickness of d or more is etched to form a metal electrode on the compound semiconductor layer. Therefore, by etching the surface of the compound semiconductor layer having a thickness of d or more, heat treatment is performed. Diffusing Z
The high resistance layer formed on the surface layer of the compound semiconductor layer can be reliably removed due to the influence of the n holes.

As a result, it becomes possible to suppress problems such as an increase in operating current, an increase in heat generation, and a decrease in device life caused by the high resistance layer formed on the surface of the compound semiconductor layer as much as possible.

[Brief description of drawings]

FIG. 1 is a graph showing the effects of the present invention.

FIG. 2 is a cross-sectional view (No. 1) for explaining the manufacturing method of the method for manufacturing the semiconductor light emitting device according to the embodiment of the invention.

FIG. 3 is a cross-sectional view (No. 2) for explaining the method of manufacturing the semiconductor light emitting device according to the embodiment of the invention.

FIG. 4 is a sectional view (No. 1) for explaining the manufacturing method of the method for manufacturing the semiconductor light emitting device according to the conventional example.

FIG. 5 is a sectional view (No. 2) for explaining the manufacturing method of the method for manufacturing the semiconductor light emitting device according to the conventional example.

[Explanation of symbols]

11 p ⁺ -GaAs substrate (semiconductor substrate) 12 p-ZnS _0.06 Se _0.94 clad layer (first clad layer) 13 Cd _0.2 Zn _0.8 Se active layer (active layer) 14 n-ZnS _0.06 Se _0.94 clad layer (second) Clad layer) 15 SiO ₂ film (passivation film) 15 A opening 16 In electrode (first electrode) 17 AuZn electrode (second electrode) 18 High reflection film 19 Low reflection film

Claims (2)

[Claims] 1. A surface layer of the compound semiconductor layer, which has been subjected to heat treatment at a temperature T for a time t after forming a compound semiconductor layer containing at least one of Zn and Se, d = [D ₀ exp {-Q / (KT)} × t] ^1/2 (D ₀ is the diffusion coefficient of Zn or Se vacancies, Q is the activation energy of Zn or Se vacancies, and k is the Boltzmann constant)
And a step of forming a metal electrode on the etched surface of the compound semiconductor layer, and a step of etching the surface of the compound semiconductor layer. 2. A first cladding layer (12) and an active layer (13) are sequentially formed on a semiconductor substrate (11), and then Z
a step of sequentially forming a second cladding layer (14) containing at least one of n and Se, and a heat treatment step of forming a passivation film (15) on the second cladding layer (14) at a temperature T for a time t. And forming an opening (15A) to expose the second cladding layer (14), and using the passivation film (15) as a mask, d = [D ₀ exp {-Q / (KT)} × t] ^1/2 (D ₀ is the diffusion coefficient of Zn or Se vacancies, Q is the activation energy of Zn or Se vacancies, and k is the Boltzmann constant)
A thickness of d or more, the step of etching the surface of the second cladding layer (14), and a second step on the second cladding layer (14) and the passivation film (15) exposed from the opening (15A). 1. A method for manufacturing a semiconductor light emitting device, comprising the step of forming a first electrode (16) and a second electrode (17) on the back surface of the semiconductor substrate (11).