JPS63142878A - semiconductor laser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a semiconductor laser that oscillates in a fundamental transverse mode and is capable of oscillating at a low threshold current density (hereinafter referred to as th).

[Conventional technology]

The structure of a conventional semiconductor laser is "XGa" in the film thickness direction.
1-XAB/GaA13O double heterostructure is used, and the refractive index in the direction parallel to the junction surface is smaller than that of the active layer.
By using the AtxG and 1-xA type semiconductor layers, we succeeded in forming the 'torque constriction' and the original confinement layer embedded. However, in this conventional technology, the embedded AtX Ga1
-χA, the resistivity of the layer is low, so current leaks outside the desired oscillation region, resulting in a problem in that it is not effective in reducing the current. Therefore, the idea was to use a high-resistivity ■-VI group semiconductor layer as the current confinement and former confinement layer, and to form stripe-like ribs to the middle depth of the cladding layer directly above the active layer. Both ends of the rib are n
-■ It was a semiconductor laser embedded with a semiconductor layer made of a conductor in an i compound.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional technology, the 9AW of the active region and ■-■
The optimal value for the layer thickness t of the cladding layer directly under the group compound semiconductor layer has not been shown, and if W and t become too large, the original oscillation of the higher-order mode will occur in the transverse mode, and the original information recording will be interrupted. There was a problem in that it was not possible to obtain a minute spot for writing and reading data in the device. Also too W
If the laser diode is small, the manufacturing method is difficult and there is a problem in that semiconductor lasers cannot be supplied in large quantities at low cost.

The present invention is intended to solve these problems.The purpose of the present invention is to completely block current leakage to areas other than the oscillation region, and to achieve oscillation in only the fundamental transverse mode by using an effective optical confinement effect. The object of the present invention is to provide a semiconductor laser that can be controlled, has a low manufacturing cost, and can stably oscillate up to high output.

[Means for solving problems]

The semiconductor laser of the present invention is a double heterojunction semiconductor laser composed of an active layer and a cladding layer made of an l[-4 compound semiconductor, and has striped ribs extending to an intermediate depth in the cladding layer immediately above the active layer. In a semiconductor laser in which both ends of the rib are embedded with a semiconductor layer made of a ■-■ group compound semiconductor, the width of the rib directly above the active layer (hereinafter referred to as W) is 1lL5 to 1α0μm, and A 1-thickness (hereinafter referred to as t) of a cladding layer immediately above the active layer, which is left between the active 1- and the semiconductor layer made of the ■-■ group semiconductor, is 0 to 2.0 μm. shall be.

〔Example〕

FIG. 1 is a main cross-sectional view of a semiconductor laser in an embodiment of the present invention. On the n-type GaA3 single crystal substrate (102), there is an n-type GaAs buffer layer (103), an n-type AtGaAs cladding layer (104), a GaA8 or AtGaA3 active layer (105), and an inverted mesa-shaped rib (106). P-type AAGaAs cladding layer formed in the mold, and (
It consists of a P-type GaAa contact layer (108), and both ends of the rib are filled with a ■-■ group compound semiconductor such as Zn8e (107).

The Z 813 layer on the top surface of the contact layer (1o8) is removed by an etching process, and 9. (109) P
A type ohmic electrode is formed. By forming an n-type ohmic electrode of (101) and passing a current between the electrodes of (109) and (101) in the forward direction, charge injection occurs in the active layer of Q (105), resulting in carrier recombination. The light emission is amplified between the cavity end faces, and the laser source is oscillated. In that case, the Zn5e layer (107) has a specific resistance of 10 MΩ9cW1 or more, and the injection current hardly flows anywhere other than the rib portion.

Therefore, laser rooting occurs only in the active layer directly under the ribs, and as no unnecessary current flows, the process is reduced. Also Z
The refractive index of n5e l- is 2.53, and the G of the active layer
The refractive index is smaller than that of aA3 or AtGaAa. Therefore, since the effective refractive index of the area immediately below the rib and other parts becomes smaller on the outside, an original confinement type waveguide is formed. Therefore, only the fundamental transverse mode of the oscillated light can be oscillated.

However, in order for only the fundamental transverse mode to oscillate, there are limits to the width W of the active region and the layer thickness t of the cladding layer directly below the Zn5e layer. FIG. 2 is a main sectional view of a semiconductor laser according to an embodiment of the present invention, and shows the locations of the above-mentioned W and t.

The length of (201) indicates W, and the length of (202) indicates t2
show. The threshold current values and transverse mode characteristics for various combinations of W and t values are summarized in the table below.

As shown in the table, the value of W is cL5~11
10 μm and the value of t is 0 to 2.0 μm, fundamental transverse mode oscillation is possible, and W is 1α0 μm.
If fc exceeds m or t exceeds 2.0 μm, higher-order mode oscillation occurs, and the oscillated light is emitted as a plurality of spots.

In the case where the cut W was smaller than 05 μm, the fabrication was markedly inner conical.

FIG. 5 is a diagram showing the manufacturing process of a semiconductor laser in an embodiment of the present invention. (301) n-type ()aAs single crystal substrate by MOCVD method D (so6) n-type GaAs
Buffer layer, (305) n-type AIG a As cladding layer, (304) GaAs or AiGa A
An S active layer, an (SOS) P-type AtGaAs cladding layer, and a (302) OP-type GaAs contact layer are sequentially laminated.

(Figure 3(b)).

Next, striped ribs are formed by a normal photo process (FIG. 5(C)).

Next, use the MOOVD method again! l) Zn of (307)
The 5e layer is embedded and grown (FIG. 3(d)).

Next, the Zn5e layer above the ribs is etched again by a photo process (No. 311(e)).

Next, (508) P type ohmic electrode, (509)
A semiconductor laser is produced by forming an n-type ohmic electrode (FIG. 5(f)).

〔Effect of the invention〕

As described above, the present invention has the following effects.

(1) Because the buried -■ group compound semiconductor has an extremely high resistivity, there is almost no leakage current outside the oscillation region, and laser oscillation is possible with a low threshold current density, so the semiconductor laser generates less heat. This facilitates the manufacture of semiconductor lasers, such as mounting them on heat sinks.

(2) By optimizing the values of W and t, the oscillation transverse mode is only the fundamental mode, and the light emission becomes a very clean spot. Therefore, when the emitted light is focused by a lens system, it can be made into a minute spot of 1 μm or less, and when reading from original information recording devices such as laser video discs and magneto-optical discs, the 8N
It can be compared.

(3) The semiconductor layer that makes up the semiconductor laser is MOC! V.D.
Since it is manufactured by the method, a semiconductor layer with uniform characteristics can be formed over a wide area, and it is excellent in mass production, and therefore, a semiconductor laser can be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a main sectional view showing an embodiment of the semiconductor laser of the present invention. FIG. 2 is a main sectional view showing one embodiment of the semiconductor laser of the present invention, and is a diagram showing W and t. FIGS. 3(a) to 3(f) are manufacturing process diagrams showing one embodiment of the semiconductor laser of the present invention. (101), (309)...n-type ohmic electrode (
102) e (501) ・"n-type GaAa single crystal substrate (105) e (306) ・"n-type GaAs buffer layer (104), (305)-n-type AAGaAs cladding layer (105), (504)...・Active layer (106), (505) ・P-type AtGaAs Clad layer (108), (502)-P-type GaAa: r
Contact layer (107), (307) - Zn8e buried layer (109 bar (308)... P-type ohmic electrode (201)... @W in active region (202)... Cladding layer directly under the Zn5e layer Applicant Seiko Epson Co., Ltd. Representative Patent Attorney Mogami...
:7 Broom 1 drawing tp/ 2nd day

Claims (1)

[Claims] In a double heterojunction semiconductor laser composed of an active layer and a cladding layer made of a III-V compound semiconductor, a striped rib is formed to a depth halfway between the cladding layer directly above the active layer, and both ends of the rib are In a semiconductor laser embedded with a semiconductor layer made of a group II-VI compound semiconductor, the width of the rib directly above the active layer (hereinafter referred to as w)
is 0.5 to 10.0 μm, and the layer thickness (hereinafter referred to as t) of the cladding layer immediately above the active layer remaining between the active layer and the semiconductor layer made of the II-VI group semiconductor is 0
A semiconductor laser characterized by having a diameter of 2.0 μm to 2.0 μm.