JPH04370993A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To realize a semiconductor laser having a low operating current value by providing an optical guide layer in contact with an active layer, and forming a current block layer having a lower refractive index than that of the clad layer in contact with the guide layer. CONSTITUTION:An n-type GaAs buffer layer 2, an n-type Ga0.45Al0.55As clad layer 3, a Ga0.9Al0.1As active layer 4, a p-type Ga0.7Al0.3As optical guide layer, and an n-type Ga0.42Al0.58As current block layer 6 are sequentially grown on an n-type GaAs substrate 1. A stripelike window is formed in the current block layer, and a p-type Ga0.45Al0.55As clad layer 7, a p-type GaAs contact layer 8 are formed. Since an optical guide layer having low AlAs mixed crystal ratio is grown in a current flowing stripe 9, an excellent growth is performed. Since a loss of a waveguide is small, an operating current value can be reduced due to the relationship between the current and an optical output.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low power consumption, low cost semiconductor laser used in optical disk memories and the like.

0002

[Prior Art] Figure 5 shows an example of the structure of a conventional semiconductor laser.
Shown below. There is an n-GaAs current blocking layer 14 having a striped window above the double hetero p-n junction including the active layer, and light is absorbed within the stripe by light absorption by this n-GaAs layer 14. That is, since light outside the stripes is absorbed by the n-GaAs layer 14, laser light exists only within the stripes, and single transverse mode laser oscillation occurs within the stripes.

0003

In recent years, with the miniaturization of optical pickups, there has been a demand for lasers with lower operating current values and lower costs. However, in the conventional structure, there is a loss in the waveguide due to absorption of laser light by the n-GaAs layer 14, and a laser with a very low operating current cannot be realized. Further, in the manufacturing process, the regrowth interface was 15(a) on GaAlAs with a high AlAs mixed crystal ratio, and the regrowth was difficult due to surface oxidation problems, making it impossible to obtain a high yield.

0004

[Means for Solving the Problems] In order to solve the above problems, in the semiconductor laser of the present invention, as shown in FIG.
There is a conductive light guide layer on the active layer, which has a refractive index lower than that of the active layer, is made of at least one layer, and facilitates regrowth, and on top of that is a conductive light guide layer, which has a conductivity type different from that of the light guide layer, and has a striped window. There is a blocking layer, and the striped window has a cladding layer that has a lower refractive index than the light guide layer and the same conductivity type as the light guide layer, and the current blocking layer has a lower refractive index than the cladding layer. ing.

[0005]

In the above structure, the refractive index of the current blocking layer is lower than the refractive index of the cladding layer, so the laser beam is confined within the stripe due to the difference in refractive index. Unlike the conventional method, confinement is not caused by absorption in the current blocking layer, so the waveguide has lower loss than the conventional method, and a laser with a low threshold value, high efficiency, and therefore low operating current can be realized. Furthermore, since the regrowth interface is grown on the light guide layer with a low AlAs mixed crystal ratio, manufacturing is easier than in the past, and a high yield can be obtained.

[0006]

Embodiment FIG. 1 shows a structural diagram of a semiconductor laser device according to an embodiment of the present invention. On an n-type GaAs substrate 1,
type GaAs buffer layer 2, n-type Ga0.45Al0
．． 55As cladding layer 3, Ga0.9Al0.1As active layer 4, p-type Ga0.7Al0.3As optical guide layer 5
and an n-type Ga0.
A 42Al0.58As current blocking layer 6 is provided, and a p-type Ga0.45Al0.55As cladding layer 7 is formed. In this structure, the current injected from the p-type GaAs contact layer 8 is confined within the stripe by the current blocking layer, and laser oscillation occurs in the active layer below the stripe. The refractive index of the p-type cladding layer of the laser beam is
Since it is larger than the refractive index of the current blocking layer, it is confined within the stripe. In this case, since there is no optical loss due to the current blocking layer, the waveguide loss is small and a semiconductor laser with a low operating current value can be obtained. FIG. 2 shows calculation results of the film thickness of the optical guide layer and the effective refractive index difference Δn between the inside and outside of the stripe. The Δn of the conventional structure is about 10-3 to 10-2, but in this structure, the refractive index difference can be freely controlled by changing the thickness of the light guide layer, and the same degree of refractive index difference can be obtained. I understand.

FIG. 3 is a manufacturing process diagram of a semiconductor laser device according to an embodiment of the present invention. As shown in FIG. 3(a), MOCVD or M
By the BE method, an n-type GaAs buffer layer 2, an n-type G
a0.45Al0.55As cladding layer 3, Ga0.9
Al0.1As active layer 4, p-type Ga0.7Al0.3
As optical guide layer 5, n-type Ga0.42Al0.58A
s current blocking layer 6 is grown. Next, as shown in FIG. 3(b), a striped window is formed in the current blocking layer by photolithography, and as shown in FIG. 3(c), MOCVD or MBE is again used to form a striped window. ,
p-type Ga0.45Al0.55As cladding layer 7, p
A type GaAs contact layer 8 is formed. Usually AlA
Growth on a substrate with a high S mixed crystal ratio is difficult due to the problem of surface oxidation, but in this case, unlike conventional stripes 9, where the current flows, growth will occur on a light guide layer with a low AlAs mixed crystal ratio. Therefore, good growth can be achieved. FIG. 4 shows the relationship between current and optical output. It can be seen that in the present invention, since the loss of the waveguide is small, the operating current value is significantly reduced compared to the conventional method. Specifically, the current value of 3 mW at room temperature was able to be reduced from the conventional 50 mA to 30 mA.

[0008]

As described above, the present invention has a light guide layer in contact with the active layer, and a current blocking layer having a lower refractive index than the cladding layer is formed in contact with the light guide layer. This realizes a semiconductor laser device whose current value is significantly lower than that of conventional devices. Also, the regrowth interface is A
Since the light guide layer has a low lAs mixed crystal ratio, regrowth can be easily performed and a high yield can be obtained. This semiconductor laser device is effective as a light source for an optical disk memory, which requires miniaturization and cost reduction of optical pickups.

[Brief explanation of drawings]

[FIG. 1] Structural diagram of a semiconductor laser in one embodiment of the present invention

[Figure 2] Diagram showing calculation results of lateral refractive index difference

[Figure 3]
Manufacturing process diagram of a semiconductor laser according to an embodiment of the present invention

[Fig. 4] Current-light output characteristic diagram of a semiconductor laser in an embodiment of the present invention

[Figure 5] Structural diagram of a conventional semiconductor laser

[Explanation of symbols]

1 n-type GaAs substrate (semiconductor substrate) 2 n-type GaAs buffer layer 3 n-type Ga0.45Al0.55As cladding layer 4 Ga0.9Al0.1As active layer (semiconductor layer I)
5 P-type Ga0.7Al0.3As optical guide layer (semiconductor layer II) 6 N-type Ga0.42Al0.58As current blocking layer (semiconductor layer III) 7 P-type Ga0.45Al0.55As cladding layer (semiconductor layer IV) 8 p-type GaAs contact layer 9 stripe section 10 n-type GaAs substrate 11 n-type GaAs buffer layer 12 n-type Ga0.45Al0.55As cladding layer 13 Ga0.9Al0.1As active layer 14 n
type GaAs current blocking layer 15 p-type Ga0.4
5Al0.55As cladding layer 15(a) Regrowth interface 16 P-type GaAs contact layer

Claims (1)

[Claims] 1. In contact with a semiconductor layer I serving as an active layer, there is a conductive semiconductor layer II having a lower refractive index than the semiconductor layer I, and in contact with the semiconductor layer II, the conductivity type is the same as that of the semiconductor layer II. Semiconductor layer I having a striped window with different
In the striped window, there is a semiconductor layer IV having a refractive index lower than that of the semiconductor layer II and having the same conductivity type as the semiconductor layer II, and the refractive index of the semiconductor layer III is lower than that of the semiconductor layer II. A semiconductor laser device characterized by having a refractive index lower than IV.