JPH02231784A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To enable fundamental-mode oscillation up to a high output by forming a semiconductor layer preventing the discontinuity of a valence band on the substrate side of a first clad layer and shaping the buried region of the side face of a stripe region in the multilayer structure of a semiconductor layer having forbidden band width larger than that of a semiconductor substrate and a semiconductor layer having forbidden band width smaller than that of the active layer of the stripe region. CONSTITUTION:A P-GaInP layer 11 is inserted between a buffer layer 2 composed of P-GaAs and a first clad layer 3 consisting of P-AlGaInP in a stripe region 10, thus preventing the discontinuity of a valence band. Since the buffer layer 2 made up of P-GaAs and a first buried layer 12 composed of P-AlGaInP are brought into contact directly in a buried region, however, there is discontinuity in the valance band. Consequently, leakage currents flowing through the first buried layer 12 consisting of P-GaInP are reduced. Since the effective refractive index of an active layer is lowered, a higher mode is not excited even when the width of the stripe region is increased. Accordingly, fundamental- mode oscillation is enabled up to a high output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a semiconductor laser, particularly a visible light semiconductor laser.

[Conventional technology]

FIG. 2 is a diagram showing a conventional visible light semiconductor laser disclosed in, for example, Japanese Patent Publication No. 62-216386. (
For convenience, p and n are reversed.] FIG. 3 is a diagram showing the lateral refractive index distribution in the active layer, which will be described later.

In Fig. 2, 11 is a p-type (p-) GaAs substrate, 2 is a p-GaAs layer which is a buffer layer, and 3 is a first cladding layer p-(A I XG a 1-x).
@． sI no. sP layer, 4 is the active layer (A
l yG a s-y)a. sI no. sP
layer, 5 is the second cladding layer n-(kl.iG a
1-x') o. sI n @. sp layer, 0
< y < X pX' is satisfied. Furthermore, 6 is an n-GaAs layer which is a contact 1 layer, 7 is a high resistance ZnSs layer which is a buried layer, 8 is a p electrode, 9 is an n electrode, 10 is a stripe region, and W is a contact layer. stripe area 10
For example, the width is 1.5μ strand. Also, 1@ in Figure 3
is the effective refractive index of the active layer 4, and n- is the refractive index of the buried layer 7.

Next, the operation will be explained.

Since the buried layer 7 has a high resistance, the electrons and holes injected from the n-electrode 9 and the p-electrode 8 are efficiently transferred to the stripe region 10.
and recombine in the active layer 4.
Emit light corresponding to the IJ band. Then, when the gain obtained by current injection exceeds the loss, laser oscillation is obtained. Since the refractive index n% of the buried layer 7 is significantly smaller than the effective refractive index n6 of the active layer 4, the laser beam emitted P4 is concentrated in the active layer 4.

[Problem to be solved by the invention]

Since the conventional semiconductor laser is configured as described above, the optical density in the active layer 4 tends to be high, and in order to obtain high output it is necessary to increase the width W of the stripe region 1o. Increasing the width W of the region 10 has the disadvantage that higher-order modes are more likely to be excited. To deal with this, when the buried layer 7 is made of Ga(1,@In●.P, this forbidden band width is less than the forbidden band width of the active layer 4 made of AjGaInP, so GaInP is made to have a high resistance. However, there was a problem in that the leakage current could not be reduced.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a semiconductor laser that can oscillate in the fundamental mode up to high output without increasing leakage current.

[Means to solve the problem]

In the semiconductor laser according to the present invention, the first
A semiconductor layer is formed on the substrate side of the cladding layer to eliminate discontinuity in the valence band, and a buried region on the side of the stripe region is made more forbidden than the semiconductor layer whose forbidden band width is larger than that of the semiconductor substrate and the active layer of the stripe region. This is a multilayer structure made of semiconductor layers with a small band width.

[Effect]

In the semiconductor laser of the present invention, the forbidden band energy of the semiconductor substrate other than the stripe region and the semiconductor layer thereon is 0.8.
The leakage current is suppressed due to discontinuity in the valence band caused by a difference of more than eV, while the effective refractive index of the active layer decreases because the laser light is absorbed by the semiconductor substrate.
Even if the width of the stripe region is increased to increase the output, higher-order modes will not be excited.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In Figure 1, the same symbols as in Figure 2 indicate the same things,
11 has a thickness of 0. 1 p an p-Gag, sln.

．． , P layer, 3 is the first cladding layer with a thickness of 1 μm ID
p 1 (A I 6, IIG a @.4) (1.1
I n @, @P layer, 4 is active layer, thickness 0.07μ
m's (A#o.sGao.e)o. sl no o.
sPJI-5 is a second cladding layer of 1 μm thick n (A l *.aG a 0.4) o. il
no. sP calendar, 6 is contact l-calendar thickness 0.5
μm n-GaAs layer, 10 has a width W = 3 pm
12 is a tenth buried layer having a thickness of 0.
1 μm p(A l o.aG & o.a) o. s
l na a. sPJIs 13 is a 2.2 μm thick n-GaAs layer which is a second buried layer, and 14 is a p-GaAs layer which is a third buried layer.

In the semiconductor laser according to the present invention, the stripe region 1
In .0, the p-GalnP layer 11 is inserted between the bar 977712 made of p-GaAs and the first cladding H3 made of p-AIGaInP. The discontinuity in the valence band disappears, but in the buried region, the buffer layer 2 consisting of p-GaAs and the p-A
Since the first buried layer 12 made of jGaInP is in direct contact with the first buried layer 12, there is a discontinuity in the fi electron band. therefore,
Leakage current flowing through the first buried layer 12 made of p-GaInP can be reduced. On the other hand, since the laser light excited in the active layer 4 is absorbed by the second buried layer 13 made of n-GaAs, the effective refractive index of the active layer 4 is n. The difference in refractive index between the buried region and the buried region is small, and even if the radiation W of the striped region 10 is increased in order to obtain high output, higher-order modes are difficult to be excited. Furthermore, the higher-order mode has a higher electric field at the periphery of the striped region 10 than the fundamental mode, so the absorption loss is large, and the oscillation threshold is higher than the fundamental mode, so it is difficult to be excited.

In the above embodiment, GaAs was used as the 20th buried layer 13 and the third buried layer 14, but AjGaAs or Ga (1.51n@,
It doesn't matter if it's gP. For example, the third embedding 1
tl4 may be p-AIGaInP.

Furthermore, an n-GaAs layer may be provided on the contact layer 6 and the third buried M14 in order to lower the ohmic resistance.

〔Effect of the invention〕

As explained above, the present invention provides the first
A semiconductor layer is formed on the substrate side of the cladding layer to form a discontinuity in the valence band, and a buried region on the side surface of the stripe region is filled with a semiconductor layer having a wider forbidden band width than the semiconductor substrate and an active layer in the stripe region. Since a semiconductor layer with a narrower forbidden band width is formed into a multi-H structure, a semiconductor laser that can oscillate in the fundamental mode up to high output can be obtained without increasing leakage current.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a semiconductor laser according to an embodiment of the present invention, FIG. 2 is a sectional view showing a conventional semiconductor laser, and FIG. 3 is a diagram showing a horizontal refractive index distribution in an active layer. In the figure, 1 is a p-GaAs substrate, 2 is a buffer rFm, and 3 is a p-AIGaInP
4 is an active layer made of AjGaInP, and 5 is n-AIGaInP.
a second cladding layer consisting of a stripe region 10;
1 is a p-GaInP layer, 12 is a first buried layer made of p-A#GaInP, 13 is a second buried layer made of n-GaAs, and 14 is made of p-GaAs. This is the third embedded layer. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masu Oiwa TA <2 others) Figure 1

Claims (1)

[Claims] In a semiconductor laser having a double heterostructure in a stripe region on a semiconductor substrate, the first
A semiconductor layer is formed on the substrate side of the cladding layer to eliminate valence band discontinuity, and a buried region on the side surface of the stripe region is formed with a semiconductor layer having a wider forbidden band width than the semiconductor substrate and an active layer of the stripe region. A semiconductor laser characterized by having a multilayer structure of semiconductor layers having a narrower bandgap width than the other layers.