JPS60130878A - Superlattice semiconductor laser - Google Patents

Abstract

PURPOSE:To improve the luminous efficiency and the life by forming the clad layer being in close contact with an active layer of double hetero junction semiconductor formed on a GaAs substrate out of superlattice in which thin films of AlAsP and GaAs are multi-laminated. CONSTITUTION:Clad layers 22 and 24 holding a GaAs active layer 23 from both sides are formed of superlattice on a GaAs substrate 21. A P-side superlattice clad layer 24 is formed of superlattice in which an AlAsP layer including P type impurity and a non-doped GaAs layer are laminated and an N-side superlattice clad layer 22 is formed of the superlattice in which an AlAs layer including N type impurity and a non-dooped GaAs layer. In such superlattice, the impurity which determines a conductive type is separated from Ga atoms spatially so that the non-luminous recombination center composed of a composite structure of Ga and the impurity is substantially reduced and the carriers exuded from the active layer 23 are also luminous-recombined thereby improving the luminous efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses Ga and AI which oscillate at wavelengths between 0.65 microns and 0.88 microns! This relates to a semiconductor laser whose main component is AsTh.

Gaklks / GaAs semiconductor lasers have already begun to be put into practical use due to their excellent characteristics and high reliability, and are used as light sources for optical disks and laser printers. / The characteristics and reliability of GaAs semiconductor lasers have been considerably improved, but in order to further improve them, the following two points need to be addressed.The first problem is that the luminous efficiency is low. The second problem is that there are many non-radiative recombination centers in the GaA/As cladding layer, and carriers that should be injected into the active layer are non-radiatively recombined in the Gp, A/As cladding layer. This is a problem of deterioration in which the optical output of a semiconductor laser decreases over time.It is known that the cause of this is an increase in dislocations in the active layer.Therefore, the purpose of the present invention is to improve the luminous efficiency. It is an object of the present invention to provide a double heterojunction semiconductor laser having an improved lifetime.According to the present invention, a double heterojunction semiconductor laser formed on a QaAs substrate has a double heterojunction semiconductor laser in close proximity to the active layer. A superlattice semiconductor laser is obtained, which is characterized in that it is formed of a superlattice in which thin films of klA s P and GaAs are stacked in multiple V1 layers.

Next, the present invention will be explained using the drawings. Figure 1 shows the conventional G
aA/AM/GaAs double heterojunction a#-conductor laser, that is, a double heterojunction part;
AlAs Clarad M12.0aAs active layer 13, P
``GaAl!A, s cladding layer 14 is laminated in an actual semiconductor laser, which has a cap layer on top of it and has a structure in which current is injected in a linear shape.
In this discussion, we have omitted the non-essential aspects. Also, the present invention, which will be described later, was treated in the same way.

Carriers are resupplied in the active layer 13 and light is emitted, but - sound 1s
The carriers in the P-GaAlAs cladding layer 14 and the N-
(]aAl!A≦2) Detailed experiments have revealed that emission recombination occurs in the Rad layer 12. This is because some of the carriers injected into the active layer 13 seep into the cladding layer, and the GaAl !The impurity contained in the As layer forms a complex with 03, and this complex acts as a non-radiative recombination center, converting the seeped carriers into non-luminescent (']'#1'r
It is a diagram showing an embodiment of the present invention. In this embodiment, as shown in FIG. 2, on a GaAs substrate 21, (3a) A8 active layer 23 is sandwiched between 2 and 2 layers are formed in a superlattice. It is formed of a superlattice in which an AJAsP layer containing P-type impurities and a non-doped GaAs layer are laminated, and
1LlksP layer containing type impurities and undoped GaAs
In such a superlattice, which is formed by a superlattice with stacked layers, the impurity that determines the isoelectric type and the Oa atom are spatially separated. Because of this, the number of bonding centers is greatly reduced, the active layer 2
The carriers seeped out from 3 are also radiatively recombined, and the luminous efficiency is improved.

In addition, in the above example, the optical subwave region = active layer, but
The same effect as the above embodiment can be obtained by using a structure in which this two-layer structure is sandwiched between cladding layers as an optical waveguide layer (optical waveguide region=active layer).

Next, the reason why the reliability is improved by using the AJAsP layer and the aAs superlattice in the cladding will be explained. Strictly speaking, there is a difference in lattice constant between 0ahlks and 0aAs, and the difference reaches 0.07% at room temperature when the Al concentration is 50%.
This difference in lattice constant causes distortion, which is not a problem with semiconductor lasers that require time, and active JF! ◎ and toro, which cause dislocations to proliferate in I13, are AlAsP and 0aAs.
When using a superlattice of 4% and setting the P concentration to 4%, the lattice constants match completely at room temperature, and the cause of dislocation proliferation disappears.

In this way, the cladding layer sandwiching the active layer is made of AlAsP.
When (1aAs is formed in a superlattice in which multiple layers are stacked), a semiconductor laser with improved luminous efficiency and improved lifetime can be obtained.

Next, the above embodiment will be explained in detail.

(The 4aAs substrate 21 is 8n (tin) doped (,)a
o using an As substrate ('On top of the JaAs substrate 21, S
e (selenium) doped (a 3 micron JaAs buffer layer was epitaxially grown on top of this layer with a thickness of 2oX), y doped (taAs M) and Be doped A of 2oλ.
lAsPJi'l'jt was repeated 500 times) f1*tt layer to obtain an N-shaped rad R. Next, non-doped OaA,s
Activity 7123 t 1000 XMf) III Sif
i'.

Furthermore, 2(1X Zn (zinc) doped A/AsP layer and 20X(D)7 doped O*As7%4 were repeated 5
00 layers were laminated.◎The growth at this time was by metal organic vapor phase epitaxy. Growth conditions are normal GaAs/0aA/A
Same as s growth, growth temperature 750℃, growth rate 5X
The double heterojunction laser thus obtained has an improved laser efficiency and an improved lifetime.
The effects of the present invention were confirmed.

In the above embodiment, the active layer was made of GaAs, but 0aA
It is clear that JAs may be used, and GaAlAsP may also be used to further reduce the difference in lattice constants. In the above embodiment, the active layer had a uniform composition, but AI! A
A superlattice of sP and GaAs may also be used.

In the above embodiment, Zn was used as the P-type impurity, but M
g (magnesium), Be (beryllium), 8i (
silicon) etc. may be used, and Se as an n-type impurity may also be used.
(Selenium) was used, but 8n (tin) or Si (silicon) may also be used.

It is clear from the spirit of the present invention that the period of the superlattice and the dimensions of the active layer, etc. in the above embodiments should not be particularly limited.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a conventional GaAs substrate/GaAs double heterojunction semiconductor laser, and FIG. 2 is a diagram illustrating an embodiment of the present invention. In the figure, 11 and 21 are GaAs substrates, ] 2 is an N fli UaA/As cladding layer, 13 and 23 are active layers, and 14 is a P-type Ga A/A
s 2 Rad layers, 2ZFiN type A/AsP/GaAs superlattice, 24 is N 2J! ! A/ASP/ (1
The aAs superlattice is shown. 1”;tt” ', ”” Patent Attorney Uchikata \,! 1. ．． ．． , , ,,,,
)\-1

Claims (1)

[Claims] In a semiconductor laser having a double heterojunction structure in which an optical waveguide region is sandwiched between cladding layers on a GaAa substrate, the two Rad layers are made of thin films of A/AsP and OaA.
1. A superlattice semiconductor laser, characterized in that s is formed of a multilayered superlattice.