JPH02305486A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:Not only to improve a second semiconductor layer in crystallinity also to lessen a series resistance between a first semiconductor layer and the second semiconductor layer by a method wherein a surface protective layer of the same material with the second semiconductor layer is continuously formed on the surface of the first semiconductor layer after the first semiconductor layer has been formed, and then the laminated piece is taken out in the air. CONSTITUTION:After an active first semiconductor layer 5 containing Al as a component has been formed, a surface protective layer 6 is formed in succession on the surface of the first semiconductor layer 5 to protect its surface, which is taken out in the air as it is, so that an oxide film is prevented from being formed on the surface of the first semiconductor layer 5. Moreover, the surface protective layer 6 is formed of the same material with a second semiconductor layer 8 which is to be formed on the first semiconductor layer 5, and an oxide film never forms on the surface of the surface protective layer 6. By this setup, the second semiconductor layer 8 which is to be formed on the surface protective layer 6 can be made excellent in crystallinity, and moreover an oxide film high in resistance is never interposed between the first and the second semiconductor layer, 5 and 8, so that the series resistance of them can be lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device such as a semiconductor laser device.

[Conventional technology]

In recent years, Aj! Demand for GaAs-based visible semiconductor laser devices is rapidly increasing as a light source for recording and reproducing optical discs such as compact discs and laser discs. In order to meet such demands, semiconductor laser devices having various structures have been researched, developed, and put into practical use.

In semiconductor laser devices, from the viewpoint of improving oscillation efficiency, it is necessary to suppress the spread of the injected current and limit the active region into which the current is injected. have been traditionally used. Various types of stripe structures have been proposed. Among them, a semiconductor laser device with an internal stripe structure in which a stripe for current confinement is provided inside the crystal performs current confinement very close to the active region. Therefore, the spread of current can be sufficiently suppressed, and therefore it is possible to realize laser oscillation with a low threshold current.

FIG. 2 shows the structure of a semiconductor laser device having an internal stripe structure as described above.

This semiconductor laser device includes an n-GaAs buffer layer 2, an n-A 12 yGa
+-yAs cladding layer 3, A I XGa+-JS active layer 4, p-A12, Gap-, As cladding layer 5, n-GaAs current blocking layer 7, and p-G
It is constructed by stacking aAs camp layers 8. 9 is a p-type ohmic electrode, and 10 is an n-type ohmic electrode.

Next, a method of manufacturing this semiconductor laser device will be explained. First, on the surface of the n-GaAs substrate 1, an n-GaAs buffer layer 'l, n-A I, a Ga1-yAsAs cladding layer 51xGa + -1IAs active layer 4, and a p-A
12 After crystal growth of the yGa+-yAs cladding layer 5, this p-A 1 , Gap-, As cladding layer 5
is etched into a mesa shape. Next, after the n-GaAs current blocking layer 7 is crystal-grown, it is taken out into the atmosphere and the n-GaAs 1i current blocking layer 7 is chemically etched into stripes to form stripes extending in a direction perpendicular to the plane of the paper in FIG. A section 11 is formed, and the p-Al, Ga1-, As cladding layer 5 is exposed at this stripe section 11.

After chemical etching, washing with water and drying are performed, followed by p.
-Grow a GaAs camp layer 8 and finally form an ohmic electrode 9.10.

In the semiconductor laser device manufactured in this way, in the portion other than the stripe portion 11, the p-GaAs cap layer 8, the n-GaAs current broaching N7, the p-A 1
Since a p-n-p junction is formed in the order of the yGa+-yAs cladding layer 5, almost no current flows, and the current is efficiently injected only into the region immediately below the stripe portion 11. In this way, the stripe portion 11 Since carriers are intensively injected into the nearby active region, laser oscillation with a low threshold current becomes possible.

[Problem to be solved by the invention]

In the method for manufacturing a semiconductor laser device as described above,
Immediately after forming the stripe portion 11 by chemically etching the n-GaAs current blocking layer 7, the p-A 1
, Gap-, As clarad layer 5 is exposed.

However, since this p-A 1 , Ga+□As cladding layer 5 is chemically very active, the p-A 1 , Gal -y^S exposed from this stripe portion 11 is
Before the formation of the p-GaAs cap layer 8, an oxide film is formed on the surface of the cladding N5 due to reaction with oxygen in the atmosphere.

For this reason, the crystallinity of the p-GaAs cap layer 8 and the like grown on this oxide layer deteriorates significantly, and the p-A I, Ga, -, As cladding layer 5 and the p-GaAs
A high resistance layer is formed at the interface with the As key 1171N8, resulting in a problem that the series resistance of the semiconductor laser device becomes significantly large.

An object of the present invention is to provide a method for manufacturing a semiconductor device in which crystallinity is improved and series resistance is reduced.

[Means to solve the problem]

The present invention includes a first semiconductor layer containing AI in its composition and a second semiconductor layer stacked on the first semiconductor layer, and after forming the first semiconductor layer, forming the second semiconductor layer. The method for manufacturing a semiconductor device includes a step of first removing the first semiconductor layer into the atmosphere, and after forming the first semiconductor layer, a surface protective layer made of the same material as the second semiconductor layer is applied to the surface of the first semiconductor layer. It is characterized in that it is formed continuously and then taken out into the atmosphere.

[Effect]

According to the configuration of the present invention, an active primary material containing Al in its composition
After the formation of the semiconductor layer, a surface protective layer is successively formed to protect the surface of the first semiconductor layer, and it is taken out into the atmosphere in this state, so that an oxide film is formed on the surface of the first semiconductor layer. can be prevented from forming. Moreover, the surface protective layer is made of the same material as the second semiconductor layer to be formed on the first semiconductor layer, and no oxide film is formed on the surface of the surface protective layer. The second semiconductor layer to be formed on the second semiconductor layer can have good crystallinity, and furthermore, an oxide film having a high resistance value is not interposed between the first and second semiconductor layers.

〔Example〕

FIG. 1 is a sectional view for explaining a method of manufacturing a semiconductor device according to an embodiment of the present invention. In FIG. 1, parts equivalent to those shown in FIG. 2 described above are designated by the same reference numerals.

In this example, a semiconductor laser device is manufactured.

First, as shown in Figure 1 (11), n-GaAs (100
) 0.5 pm n-GaAs buffer layer 2. 1.0 μm n-A II, Ga+-yAs cladding layer 3. 0.08 μm Q 1 xGa+□As active N4, first semiconductor on substrate 1 The p-A layer is 1,0 pm.
1, Ga, -, As cladding N5. A p-GaAs surface protective layer 6 with a thickness of 0.01 pm is sequentially grown by MOCVD.

Next, as shown in FIG. 1 (2), p-A 1 , Ga,
The width of the yAs cladding N5 and the p-GaAs surface protection layer 6 is 5 μm.

Chemically etched into a mesa shape with a height of 0.8 μm.

Next, as shown in Figure 1 (3), 0.5 p m of n
- Crystal growth of GaAs current blocking layer 7;

Next, as shown in FIG. 1(4), only the upper part of the mesa-shaped portion of the n-GaAs current blocking layer 7 is removed by 0.4 mm from the surface.
A stripe portion 11 is formed by chemical etching by 5 μm.

Finally, as shown in FIG. 1 (5), a 0.5 μm p-GaAs camp N8, which is the second semiconductor layer, is grown as a crystal.
Furthermore, a p-type ohmic electrode 9 and an n-type ohmic electrode i10 are formed.

According to such a manufacturing method, the upper part of the mesa-shaped portion which is to become a current path on the substrate surface immediately after chemical etching (FIG. 1 (2)) is formed by the p-GaAs cap layer 8.
This part is covered with a thin p-GaAs surface protection layer 6 made of the same material as the stripe section 11, and therefore this part is hardly oxidized.
The aAs current blocking layer 7, the p-GaAs camp layer 8, etc. can have good crystallinity. p-
Since GaAs surface-retaining WN6 does not contain Al in its composition and is therefore not chemically active, no high resistance layer is formed on its surface.

Moreover, in the process of crystal growth of the p-GaAs cap layer 8, the p-type dopant 1 from this p-GaAs camp N8
Thermal diffusion of -Zn occurs, and the n-GaAs current blocking layer 7 left thinly above the mesa-shaped portion is modified to be p-type. Therefore, in the stripe section 11, pn-p
No bond is formed.

According to experiments conducted by the inventors, the semiconductor laser device manufactured as described above has good crystallinity and extremely low series resistance.
Forward current of 10 m of internal stripe type semiconductor laser device (cavity length 250 μm) manufactured based on this example
The series resistance at time A is 130Ω, and the series resistance under the same conditions is 180 to 2
It was far below 00Ω.

In the above embodiment, when etching the n-GaAs1i style blocking layer 7 to form the stripe portion 11,
In this 1-GaA5ii style profking layer 7, a thin portion is left on the p-GaAs surface protection layer 6, but when forming the stripe portion 11, the p-GaAs surface protection layer 7 is removed from the stripe portion 11. Layer 6 may be exposed.

Note that the present invention is not limited to GaAs/A I GaAs semiconductor laser devices, but can be widely applied to semiconductor devices manufactured using any compound semiconductor containing Al.

〔Effect of the invention〕

According to the method for manufacturing a semiconductor device of the present invention, after the formation of the active first semiconductor layer containing AI in its composition, a surface protection layer that protects the surface of the first semiconductor layer is successively formed; Since it is taken out into the atmosphere in this state, it is possible to prevent an oxide film from being formed on the surface of the first semiconductor layer.

Moreover, the surface is protected! The layer is made of the same material as the second semiconductor layer to be formed on the first semiconductor layer, and no oxide film is formed on the surface of this surface protection layer. Therefore, the second semiconductor layer to be formed on the surface protective layer can have good crystallinity, and an oxide film having a high resistance value is interposed between the first and second semiconductor layers. As a result, it is possible to improve the crystallinity of the semiconductor device, and to significantly reduce the series resistance of the semiconductor device, thereby reducing the acclimatization power. become.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining a method of manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a sectional view showing the basic structure of a conventionally used semiconductor laser device. 5...p-A 1 yGa+-, As clad N(
(first semiconductor layer), 6 .=p-GaAs surface protection layer, 7 .=n-GaAs current blocking layer, 8...
p-GaAs cap J! ! (Second semiconductor layer) Figure 1

Claims (1)

[Scope of Claims] Comprising a first semiconductor layer containing Al in its composition and a second semiconductor layer stacked on the first semiconductor layer, the second semiconductor layer is formed after the first semiconductor layer is formed. In the method for manufacturing a semiconductor device, the method includes a step of exposing the first semiconductor layer to the atmosphere before forming the first semiconductor layer. A method for manufacturing a semiconductor device, characterized in that it is formed continuously on a surface and then taken out into the atmosphere.