JPS62186581A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To manufacture, with high reproducibility, a laser device which oscillates in a fundamental transversal mode with a small current, by forming a current blocking multilayer possessing a stripe type window at a specified position on a clad layer on an active layer. CONSTITUTION:On one side of an N-type GaAs substrate 1, the following layers are formed in order; a buffer layer 2, a clad layer 3, an active layer 4, a clad layer 5, a current blocking layer 6, a clad layer 8, a contact layer 9 and an electrode 10. On the other surface, an electrode 11 is formed. The current blocking layer 6 has a multilayer structure wherein an N-type GaAs layer 12 and a GaAl As barrier layer 13 are alternately formed and a stripe type window is arranged at a specified position. Thereby, a laser device which oscillates in a fundamental transversal mode with a small current can be manufactured with high reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor laser device, which has been rapidly used as a light source for various electronic devices and optical devices in recent years, and is in increasing demand.

(Prior Art) Important performances required of semiconductor lasers as coherent light sources for electronic and optical equipment include low current operation and fundamental transverse mode oscillation. In order to achieve these performances, it is necessary to suppress the spread and confine the current so as to concentrate it near the active region where the laser light propagates. A semiconductor laser with such a structure inside is usually called an internal stripe type laser. (For example, Compound Semiconductor Devices (Il) edited by Tetsuji Imai et al.
, 214-p., 215) Hereinafter, the conventional internal stripe type radar as described above will be explained with reference to the drawings.

In FIG. 4, 1 is an n-type GaAs substrate, 2 is an n-type GaAs substrate, and 2 is an n-type GaAs substrate.
As buffer layer, 3 is n-type AtGaAs cladding layer, 4
is an AtGaAs active layer, 5 is a p-type AAs cladding layer, 14 is an n-WGaAs current blocking layer, and 8 is a p-type AJ! G
aAs cladding layer, 9 a p-type GaAs contact layer, 1
0 is a p-side ohmic electrode, and 11 is an n-side ohmic electrode.

The creation method and operation of the internal stripe type laser configured as described above will be briefly described below.

The internal stripe type resistor is formed in two crystal growth steps. Here, the crystal growth process K MOCVD method is used. As the first crystal growth, Kn-type G is grown on the n-type substrate 1.
aAs buffer layer 2, n-type AtGaAs cladding layer 3,
A,/1 GaAs active layer 4, p-type AIG aAs cladding layer 5, and n-type GaAs current blocking layer 14 are grown in sequence. The growth conditions were as follows: a growth temperature of 800° C., a supply molar ratio (V/III ratio) of the group II element to the group III element (V/III ratio), and a growth rate of 5 tt. Next, stripes with a width of 5 μm are formed at a pitch of 250 μm on the grown n-type GaAs layer using a photoresist film. At this time, the stripe is n-type G
It should be parallel to the (011) direction of the aAs substrate.

By chemical etching, the n-type GaAs current blocking layer 14 is completely removed by the entire internal stripe width W, and the p-type A1
．． GaAs cladding layer 5 gold is exposed. Furthermore, after this internal strife has been completely formed, a second crystal growth is performed by the Ni0CVD method. That is, p-type A7GaA
An s-cladding layer 8 and a p-type GaAs contact layer 9 are grown in sequence. Ohmic voltage vjL1 on the p side and n side respectively
o, 11 v, (formation p, element is completed.

When a voltage of ('') is applied to the p-side electrode 10 and a voltage of (→) is applied to the n-side electrode 11, the n-type GaAs current blocking layer 14 and the p-type A/Ja
A voltage is applied to the p-n junction part of the interface of the As cladding layer 5 in the reverse direction and to the other parts in the forward direction, and the injected current flows only from the internal stripe width W and flows into the active layer 4 directly below it. Current concentration results in low current operation fundamental transverse mode oscillation.

(Problem to be solved by the invention) However, in the double internal stripe structure, n
If the layer thickness or gearia concentration of the GaAs current blocking layer 14 varies within one laser element or within the wafer surface, light emission from the active layer 5 will cause n-type Ga
The force of the diffusion distance of the hole in the electron-hole pair generated in the A s current blocking layer 14 is 11 type Ga, As current blocking layer] 4
[N-type layer aAs current block]
] Te layer 14 p type! 4 aA s Accumulated near the boundary with the cladding layer 5.8, and as a result, the barrier due to the pn junction in the opposite direction that formed the internal stripe structure expires.
~, the internal stripe structure is lost. Therefore, the operating current value required to obtain the same optical output increases (and the current stripe width substantially increases), which increases the light emitting portion in the active region and increases the oscillation of higher-order modes. First, there was the problem of multimode oscillation.

In view of the above-mentioned problems, the present invention provides that even if the layer thickness and carrier concentration of the n-type GaAs current blocking layer vary, the electrons generated by light emission from the active layer in the n-type GaAs current blocking layer The object of the present invention is to provide a semiconductor radar device that effectively recombines holes in hole pairs with electrons, completely prevents deterioration of the internal stripe structure, has good reproducibility, operates at low current, and oscillates in a fundamental transverse mode.

(Means for Solving the Problems) In order to solve the above problems, the semiconductor laser device of the present invention has a double heterostructure including an active layer on a substrate and a cladding layer on the active layer. A multilayer thin film is formed, and on the cladding layer of the multilayer thin film, three or more layers including at least one layer having a conductivity type opposite to that of the cladding layer and having a band gap smaller than any other layer are formed. It has a structure in which a multilayer current blocking layer having stripe-shaped windows at predetermined positions is formed.

(Function) With this configuration, it is possible to realize a semiconductor laser device having an internal stripe structure that operates at low current with good reproducibility and oscillates in a fundamental transverse mode.

(Example) Hereinafter, an example of the present invention will be described with reference to all the drawings.

FIG. 1 shows a cross section of a semiconductor radar device according to an embodiment of the present invention. In FIG. 1, 1 is n-type GaAs
Substrate, 2 is n-type GaAs buffer layer, 3 is n-type AtGa
, A++ cladding layer, 4 is AtGaAs layer, 5 is p-type A
1-GaAs cladding layer, 6 a multilayer current blocking layer, 8 a p-type AAs cladding layer, 9 a p-type GaAs contact layer, 10 a p-side half-mic electrode, and 11 an n-side ohmic electrode.

FIG. 2 is a diagram showing details of the multilayer current blocking layer 6 of FIG. 1, where 5 is a p-type AIG aAs cladding layer, 8 is a p-type
type AtGaAs cladding layer, 12 is an n-type GaAs layer, 1
3 is a GaAtAs i4 rear layer. Further, FIG. 3 is a diagram showing the manufacturing process of the semiconductor laser device of this example.
1 is an n-type GaAs substrate, 5 is a p-type AtGaAs cladding layer, 6 is a multilayer current blocking layer, and 7 is a photoresist film.

Next, a method for manufacturing the semiconductor laser device having the above configuration will be explained.

Here, an n-type GaAs substrate is used as the substrate.

First, n-type GaAs was grown on this n-type GaAs substrate 1 by metal organic vapor phase epitaxial growth (MOCVD).
Buffer layer 2'& 0.5 μm, n-type AZXG a 1-
XA s cladding layer 3 Total 1.2 μm 1AAyG
a, -yAs active layer 4 (0≦y<x) io, 1 μm, p
Type AtXGa, -XAs cladding layer 5'tO, 3μm
, furthermore, as shown in Fig. 2, a 0.3 μm thick n-type Ga
As layer 12 (carrier concentration ~5X1018crn-3)
GaAJ with 3 layers and a thickness of 0.05 μm! , two layers of As barrier layers 13 are epitaxially grown alternately to form a total of 5 layers.
A multilayer current blocking layer 6 with a layer thickness of 1 μm is grown. An example of the crystal growth conditions at this time is that the growth temperature is 75
0°C, growth rate 3 μm/hour, supply molar ratio of group Ⅰ elements to group Ⅰ elements (V/IIT ratio) is 2o, total gas flow rate is 5
It is 117 minutes.

Next, as shown in FIG.
11) Stripes of photoresist films 7 having a width of 50 μm and a pitch of 250 μm are formed on the current blocking layer 6, which is a full multilayer structure. Then, by chemical etching, a part of the multilayer current blocking layer 6 is etched in the depth direction until the surface of the p-type Al aAs cladding layer 5 is exposed, thereby forming a window.

After cleaning the surface, p-type Al 2
G a 1, A s cladding layer 8 k 1.2 Jim
, pm, GaAs contact layer 9 e 1.5
The film is grown to a thickness of μm by MOCVD. The growth conditions are the same as those for the first crystal growth.

An n-side ohmic electrode 11 is formed using AuGeNi on the n-type GaAs substrate 1, and an Au layer is formed on the p-side GaAs contact layer 9.
A p-side ohmic electrode 10 is formed from Zn, and the device is completed.

When all of the fabricated semiconductor laser elements are mounted and operated by flowing a current, the current is narrowed to a stripe width W shown in FIG. An example of typical laser characteristics within a wafer is expressed as a threshold current value of 35 m at w = 2 μm.
A low threshold current value of A was obtained, and the oscillation was stable fundamental transverse mode oscillation. As a result of fabricating and comparing a conventional internal stripe type laser having a single current blocking layer as shown in FIG. 4, the dispersion of the threshold current value in 30 elements was found to be about V3 for the inventive laser as compared to the conventional one. , the effective diffusion length of minority carriers was shortened, indicating that the current blocking effect was working effectively.

In this embodiment, GaAs-based and GaAtAs-based semiconductor lasers have been described, but the present invention can be similarly applied to semiconductor laser devices made of compound semiconductors including InP-based and other multi-component mixed crystal systems. can. Furthermore, one of the multilayer current blocking layers exhibits a conductivity type opposite to that of the substrate.
Except for the GaAs layer, either a non-doped p-type layer or an n-type layer may be used.

Either A'tGaAs may be used.

(Effects of the Invention) As explained above, according to the present invention, it is possible to easily form an internal stripe structure with good reproducibility, and as a result, a high-performance semiconductor that oscillates in the fundamental transverse mode with a low threshold current value. A laser device can be provided, and its practical effects are remarkable.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a semiconductor laser device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a multilayer current blocking layer of the same embodiment.
FIG. 3 is a diagram showing the manufacturing process of the same embodiment, and FIG. 4 is a sectional view of a conventional semiconductor laser device. 1 ・= n-type GaAs substrate, 2 = n WGaAs
Buffer layer, 3- n-type AtGaAs cladding layer, 4
= AbaAs active layer, 5... p-type AtGaAs cladding layer, 6... multilayer current blocking layer, 7... photoresist film, 8... p-type AIG aAs cladding layer, 9
...p-type GaAs contact layer, 10...p-side ohmic electrode, 11...n-side ohmic electrode, 12--
- n-type GaAs layer, 13- GaAtAs barrier layer,
W: Internal stripe width. Figure 1 W Internal strut 4 Fuku Figure 3 Figure 4 114

Claims (1)

[Claims] A multilayer thin film formed on a substrate and consisting of a double heterostructure including an active layer and having a cladding layer on the active layer; A semiconductor comprising three or more layers including at least one layer having a band gap smaller than any other layer, and further comprising a multilayer current blocking layer having striped windows at predetermined positions. laser equipment.