JPH05175596A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To lower oscillation threshold current by preventing current flowing from a clad layer through a buried layer so that current can be concentrated on an active layer, in a semiconductor laser device which has ridge-type buried mechanism. CONSTITUTION:On an n<+>-InP substrate 11 are formed an n<->-In0.6Ga0.4As0.9P0.1 active layer (lambda=1.55mum) 12 and a p-In0.92Ga0.08As0.18P0.82 clad layer (lambda=1.0mum) 13. These layers are buried by p-InP buried layers 14a and 14b, and n-InP buried layers 15a and 15b, all of which have the same material as the substrate 11. The forbidden band of the clad layer 13 is 1.24eV. The band gap of the buried layers 14a and 14b is 1.35eV. Therefore, the potential barrier of 0.7eV to holes is formed at the interface, formed. As a result, flowing of holes from the clad layer 13 to the buried layers 14a and 14b is restrained, and oscillation threshold current is lowered because current concentrates in the active layer 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device, and more particularly to a semiconductor laser device having a ridge type buried structure suitable for use in 1 .mu.m band optical communication.

[0002]

2. Description of the Related Art FIG. 4 is a view showing a cross section of a main part of a general structure of an InGaAsP ridge type buried structure semiconductor laser device.

In the figure, 21 is an n ⁺ -InP substrate and 22 is n.
_{^{- -In 0.6 Ga 0.4 As 0.9 P}} 0. 1 active layer (lambda = 1.
55 μm), 23 is a p-InP clad layer, and 24 is a p-
InP buried layer, 25 is n-InP buried layer, 26
Is a p-InP clad layer, 27 is p ⁺ -In _0.71 Ga
_0.29 As _0.66 P _0.34 contact layer (λ = 1.3 μm).

The active layer 22 is composed of In _0.6 Ga _0.4 As _0.9 P _0.1 having the same lattice constant as the substrate 21 and a forbidden band width corresponding to an oscillation wavelength of 1.55 μm. The cladding layer 23 immediately above the active layer 22 is made of p-InP. The active layer 22 and the cladding layer 23 are
It is embedded by the p-InP burying layer 24 and the n-InP burying layer 25.

In addition to this conventional example, in addition to a structure in which the buried layer is made of pn junction type InP, a structure in which ZnSeTe having a larger forbidden band width than the clad layer 23 is used as the buried layer is also proposed.

[0006]

A semiconductor laser device is required to have a small oscillation threshold current.
In order to reduce the oscillation threshold current, the current is set to the active layer 22.
Need to focus on. However, the conventional semiconductor laser device has a problem that it is difficult to reduce the oscillation threshold current because a leakage current flows from the cladding layer 23 through the buried layer 24.

In a semiconductor laser device having a structure in which ZnSeTe is used for burying, the burying layer is a substrate (II
II-V composed of elements completely different from I-V semiconductors)
Since it is a Group I semiconductor and is a mixed crystal, it is difficult to obtain an epitaxial layer with excellent crystallinity.

The present invention solves the above-mentioned problems and prevents current from flowing from the cladding layer through the buried layer so that current can be concentrated in the active layer and lowers the oscillation threshold current. It is an object of the present invention to provide a semiconductor laser device capable of achieving the above, particularly a semiconductor laser device having a ridge-type buried structure.

[0009]

In order to achieve the above object, a semiconductor laser device according to the present invention is constructed as follows.

(1) A semiconductor laser device in which the active layer is a ridge type and has a buried structure, wherein the buried layer is
It is made of the same material as the substrate of different conductivity type, and the clad layer directly above the active layer is made of a material having a forbidden band width smaller than that of the material forming the buried layer.

More specifically, (2) the substrate is made of n-type InP, the buried layer is made of pn junction type InP, and the clad layer immediately above the active layer constitutes the active layer. Of InGaAsP having a band gap larger than that of InGaAsP
It is composed of P.

Or (3) the substrate is made of n-type InP, the buried layer is made of high-resistance InP, and the clad layer directly above the active layer is a band gap of InGaAsP which constitutes the active layer. It is composed of InGaAsP having a composition having a forbidden band width larger than the width.

[0013]

In the semiconductor laser device having the ridge-type buried structure according to the present invention, the buried layer is made of the same material as that of the substrates having different conductivity types, and the clad layer immediately above the active layer is prohibited from the material of the buried layer. It is made of a material having a forbidden band width smaller than the band width.

As a result, since the buried layer is made of the same material as the substrate, it is possible to easily obtain a material having excellent crystallinity. Then, as shown in FIG. 2, a potential barrier for holes, which are majority carriers, is formed at the interface between the clad layer and the buried layer, so that the flow of holes from the clad layer to the buried layer can be suppressed. Therefore, it becomes possible to reduce the leakage current. As a result, the oscillation threshold current can be reduced.

[0015]

EXAMPLES Example 1 FIG. 1 is a diagram showing Example 1.

In the figure, 11 is n⁺-InP substrate, 12 is n
^--In_0.6Ga_0.4As_0.9P_{0. 1}Active layer (λ = 1.
55 μm), 13 is p-In_0.92Ga_0.08As_0.18P
_0.82Clad layer (λ = 1.0 μm), 14 is p-InP
Buried layer, 15 is n-InP buried layer, 16 is p-
InP clad layer, 17 is p⁺-In_0.71Ga_0.29As
_0.66P_0.34The contact layer (λ = 1.3 μm).

A method of manufacturing the semiconductor laser device having the ridge type buried structure according to the present invention shown in FIG. 1 will be described below. On the n ⁺ -InP substrate 11, MOVPE (Metal Or
ganic Vapor Phase Epitaxy) method
μm n ⁻ −In _0.6 Ga _0.4 As _0.9 P _0.1 active layer (λ = 1.55 μm) 12 and 0.5 μm thick p−
In _0.92 Ga _0.08 As _0.18 P _0.82 cladding layer (λ = 1.
0 μm) 13 is grown.

On the surface of the growth layer, for example, Si having a width of 3 μm
After attaching an O ₂ film and performing mesa etching, the p-InP burying layer 14 and the n-InP burying layer 15 are subjected to MOV.
It grows by the PE method.

After removing the SiO ₂ film by etching,
The p-InP clad layer 16 and the p ⁺ -In _0.71 Ga _0.29 As _0.66 P _0.34 contact layer (λ = 1.3 μm) 17 are grown by the MOVPE method.

The forbidden band width of the clad layer 13 is 1.24 eV.
Therefore, the forbidden band width of the buried layer 14 is 1.35 eV. Therefore, a potential barrier of about 0.7 eV for holes is formed at the interface between the clad layer 13 and the buried layer 14. This suppresses the inflow of holes from the clad layer 13 into the buried layer 14. As a result, the current can be concentrated in the active layer 12, so that the oscillation threshold current can be reduced.

(Second Embodiment) FIG. 3 is a diagram showing a second embodiment.
is there. In the figure, 11 is n⁺-InP substrate, 12 is n^--I
n_0.6Ga_0.4As_0.9P_{0. 1}Active layer (λ = 1.55μ
m) and 13 are p-In_0.92Ga_0.08As_0.18P_0.82Kura
Dead layer (λ = 1.0 μm), 16 is p-InP clad
Layer, 17 is p⁺-In _0.71Ga_0.29As_0.66P_0.34Con
Tact layer (λ = 1.3 μm), 18 is filled with high resistance InP
It is a mixed layer.

In the first embodiment, the pn junction type burying is performed by the p-InP burying layer 14 and the n-InP burying layer 15, but in this embodiment, the high resistance In
The P burying layer 18 is used for burying.

Also in the structure of this embodiment, like the first embodiment, the inflow of holes from the cladding layer 13 to the buried layer 18 is suppressed. As a result, the current can be concentrated in the active layer 12, so that the oscillation threshold current can be reduced.

[0024]

According to the present invention, in a semiconductor laser device having a ridge type buried structure, it is possible to prevent a current from flowing from the cladding layer through the buried layer, so that the current is concentrated in the active layer. Therefore, the oscillation threshold current can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment.

FIG. 2 is a band diagram of an interface between a clad layer and a buried layer.

FIG. 3 is a diagram showing a second embodiment.

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

11 n ⁺ -InP substrate 12 n ^--In _0.6 Ga _0.4 As _0.9 P _0.1 active layer (λ = 1.55 μm) 13 p-In _0.92 Ga _0.08 As _0.18 P _0.82 clad layer (λ = 1.0 μm) 14 p- InP buried layer 15 n-InP buried layer 16 p-InP clad layer 17 p ⁺ -In _0.71 Ga _0.29 As _0.66 P _0.34 Contact layer (λ = 1.3 μm)

Claims (3)

[Claims] 1. A semiconductor laser device in which an active layer is a ridge type and has a buried structure, wherein the buried layer is made of the same material as a substrate having a different conductivity type, and the clad layer directly above the active layer is buried. A semiconductor laser device comprising a material having a forbidden band width smaller than a forbidden band width of a material forming the layer. 2. The substrate according to claim 1, wherein the substrate is made of n-type InP, the buried layer is made of pn junction type InP, and the clad layer immediately above the active layer is made of InGa.
A composition with a forbidden band larger than the forbidden band of AsP
A semiconductor laser device comprising nGaAsP. 3. The InGa according to claim 1, wherein the substrate is made of n-type InP, the buried layer is made of high-resistance InP, and the clad layer directly above the active layer constitutes the active layer.
A composition with a forbidden band larger than the forbidden band of AsP
A semiconductor laser device comprising nGaAsP.