JPH08307010A - Semiconductor laser - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent reduction of device life of semiconductor lasers. [Structure] A first conductivity type clad layer is formed on an active layer formed on a substrate, and the upper portion is formed into a ridge-shaped stripe. The ridge-shaped stripe extends in the [110] direction, and the angle between its side surface and the substrate surface is 100 degrees or less. The second conductivity type semiconductor layer filling the side surface of the ridge-shaped stripe is formed of SiO ₂ or Si ₃ N _{4 on the} upper surface of the stripe.
Since it is formed by the MOCVD method or the like with the mask left unetched, it is formed substantially flat with respect to the upper surface of the stripe without covering the upper surface thereof. [Effect] Since it is possible to suppress the generation of crystal defects in the electrically and optically active regions of the semiconductor laser when the ridge-shaped stripe and the layer for burying the ridge stripe are formed, it is possible to suppress the decrease in the optical output of the semiconductor laser and to extend the life. Can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser capable of stably oscillating in a transverse mode, and in particular, it has a small leakage current outside the light emitting region of the semiconductor laser and has crystal defects introduced into the light emitting region. The present invention relates to a semiconductor laser whose reliability is improved by making it harder to operate.

[0002]

2. Description of the Related Art A conventional self-aligned structure semiconductor laser is
J. J. The structure is as shown in Coleman et al. That is, as shown in FIG. 2, n-type GaAs
On the substrate 1, an n- (GaAl) As cladding layer 2, an undoped (GaAl) As active layer 3, and a p- (GaAl) As layer 3 are formed.
The clad layer 4 and the n-GaAs light absorption layer 5 are formed, a part of the light absorption layer is removed by etching to form stripes, and the p- (GaAl) As6 is buried, and then the p-GaAs layer 7 for forming electrodes is formed. (Coleman et al., Applied Physics Letter, Vol. 37, Vol. 2)
P. 62 1980 (JJ Coleman et al., Appl. Phys.
Lett. Vol 37 (3), p.262, 1980)), the current confinement and the formation of the waveguide were performed at the same time by the light absorption layer, but this structure was used in the thermal non-equilibrium state such as MOCVD and MBE. In the case of forming by using the above-mentioned crystal growth, the crystal reliability accompanying the crystal growth on the step and the growth interface of the double growth are in the electrically and optically active regions, which deteriorates the reliability of the device. .

[0003]

DISCLOSURE OF THE INVENTION The present invention has problems of a conventional structure of a self-aligned semiconductor laser, a crystal defect accompanying crystal growth on a substrate having a step, and a defect of a growth interface of double growth. Another object of the present invention is to provide a semiconductor laser capable of preventing a reduction in device life due to the above.

[0004]

DISCLOSURE OF THE INVENTION The present invention has problems of a conventional structure of a self-aligned semiconductor laser, a crystal defect accompanying crystal growth on a substrate having a step, and a defect of a growth interface of double growth. In order to prevent the reduction of the device life due to the
Instead of filling with, the p-type clad layer is etched using an insulator mask such as SiO ₂ or Si ₃ N ₄ provided in a stripe shape on the p-type clad layer outside the stripe,
A III-V group compound semiconductor material having a zinc blende type crystal structure in which a waveguide is formed by burying with GaAs by MOCVD method in which crystal growth does not occur on an insulator but only outside the stripe is performed. The present invention relates to the semiconductor laser used.

[0005]

According to the present invention, the clad layer having the ridge-shaped stripe can be formed on the active layer by one-time crystal growth. Therefore, it is possible to form a growth interface on a substrate having a step or a growth interface by two-time growth. A defect-free self-aligned semiconductor laser can be realized.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 shows the sectional structure of a semiconductor laser according to this example. The manufacturing process of this structure is as follows.

An n-Ga _0.55 Al _0.45 As clad layer 2, an undoped Ga _0.86 Al _0.14 As active layer 3 and a p-Ga _0.55 Al layer are formed on an n-GaAs substrate 1 by atmospheric pressure MOCVD.
_{After the 0.45} As clad layer 4 and the p-GaAs cap layer 8 were sequentially crystal-grown, a SiO ₂ mask 13 was provided using a normal photolithographic technique, and a phosphoric acid-based etching solution was used to form a p-type clad layer outside the stripes. 0.1 to 0.
Etching was performed leaving 3 μm. FIG. 3 shows a cross-sectional structure of the device at this stage. The structure produced in this way
It was embedded again with n-GaAs 9 by the MOCVD method. Here, when the stripe orientation is set to the [1-10] direction, as shown in FIG. 4, since growth occurs from the ridge side surface and sharp protrusions are formed on both sides of the stripe, the stripe orientation is set to the [110] direction. It is necessary to set the angle 14 of the ridge side surface with respect to the substrate surface to 100 degrees or less by a method such as using dry etching, and preferably to make the ridge shape an inverted trapezoid as shown in the figure. Is. In this case, the SiO ₂ film remained exposed due to the characteristics of the MOCVD method in which crystal growth did not occur on the SiO ₂ film and could be removed by a hydrofluoric acid-based etching solution after the buried growth. In this structure, Cr / Au10 is used as the p electrode and AuGeNi / Cr / is used as the n electrode.
Au11 was vapor-deposited and cut into a 300 μm square to form a laser chip.

Example 2 As a second example, instead of using p-Ga _0.55 Al _0.45 As layer 4 as the p-type clad layer, p-Ga _0.6 Al _0.4 As layer 4 and p-Ga _0.35 Al are used.
A device having a double-layered structure of _0.65 As layer 12 and having a structure as shown in FIG. Here, was 0.1~0.3μm the thickness of the p-Ga _0.7 Al _{0. 3} As layer 4. In this structure, by using an iodine-based etching solution, p-Ga _0.5 Al _0.5
The As layer 12 can be selectively removed with respect to the p-Ga _0.6 Al _0.4 As layer 4. Hereinafter, a semiconductor laser chip was manufactured by the same process as in Example 1.

[0010]

According to the present invention, since the generation of crystal defects in the electrically and optically active regions of the semiconductor laser can be suppressed, it is possible to prevent the shortening of the life of the semiconductor laser device, and therefore the reliability of the device is high. A semiconductor laser can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional structure diagram of a semiconductor laser of Example 1.

FIG. 2 is a sectional structural view of a conventional self-aligned semiconductor laser.

FIG. 3 is a sectional structural view of a semiconductor laser of Example 1 before buried growth.

FIG. 4 is a view showing a sectional structure when buried growth is performed on a stripe in the <110> direction.

FIG. 5 is a sectional structural view of a semiconductor laser of Example 2.

[Explanation of symbols]

1 ... n-GaAs substrate, 2 ... n-Ga _0.55 Al _0.45 As
Cladding layer, 3 ... Undoped Ga _0.86 Al _0.14 As active layer, 4 ... p-Ga _0.55 Al _0.45 As cladding layer, 5 ... p
-GaAs light absorption layer, 6 ... p- (GaAl) As layer, 7
... p-GaAs, 8 ... p-GaAs cap layer, 9 ... n
-GaAs layer, 10 ... Cr / Au, 11 ... AuGeNi
/ Cr / Au, 12 ... p-Ga _0.5 Al _0.5 As layer, 13
... SiO ₂ mask, 14 ... angle formed between the substrate and the side surface of the ridge.

Claims (1)

[Claims] 1. A semiconductor substrate, an active layer formed on the semiconductor substrate, a first-conductivity-type clad layer formed on the active layer and having a stripe-shaped ridge portion, and a stripe-shaped clad layer. The ridge portion is formed so as to fill the side surface of the ridge portion and includes a semiconductor layer of the second conductivity type.
0] and the angle of its side surface with respect to the surface of the semiconductor substrate is 100 degrees or less.