JPS5990979A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain the semiconductor laser, from which leakage currents are not generated and an optical output thereof is large, by forming a current stopping layer containing an N type semiconductor layer with forbidden band width larger than that of a P type semiconductor substrate and a striped groove, from which the current stopping layer is emitted, onto the semiconductor substrate and forming the region of the upper active layer of the striped groove so as to function as a main light-emitting region. CONSTITUTION:The first current stopping layer 12 consisting of N type Al0.4Ga0.6As and the second current stopping layer 13 consisting of N type GaAs are formed onto the P type GaAs substrate 11, and a P type clad layer 14 consisting of P type Al0.4Ga0.6As, an active layer 15 consisting of Al0.15Ga0.85As and an N type clad layer 16 consisting of N type Al0.6Ga0.6As are further formed. Consequently, a hetero-barrier to holes is generated in the emitter junction of a transistor 20, the implantation efficiency of an emitter lowers extremely, and the gains of the transistor 20 reduce extremely. When the scattered light of a laser oscillation is absorbed to the second current stopping layer 13, currents corresponding to extinction light flow, but they are not multiplied by the transistor 20, and large leakage currents are not generated. Accordingly, leakage currents bypassing the active layer are little even on a large implantation, and a large optical output is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser that uses a P-type semiconductor as a substrate, has a stable transverse mode, and has a large optical output.

Conventionally, the first semiconductor laser using a P-type semiconductor substrate
[There is a V818 laser as shown in J.

In the following, to simplify the discussion, we will use GaAs as a P-type semiconductor substrate.
This will be explained using an example using . In Figure 1, 1 is P-type GaA
s substrate, 2 is made of N-type GaAs, and current blocking layer 3 is made of Al.
A P-type cladding layer made of GaAs, 4 an active layer made of AlGaAs, and 5 an assed PN made of AlGaAs.
By creating a junction, only the active layer 4 above the channel portion 8 can be effectively excited with current. However, as the implantation amount is gradually increased, the optical output increases, and a part of the optical output is scattered and absorbed by the current blocking layer 2. At this time, the P-type cladding layer 3, the current blocking layer 2,
The P-type GaAs substrate 1 operates as a PNP transistor 9, and when it is injected into the current blocking layer 2 corresponding to the base, it has the effect of multiplying the current, causing the current to become P-type GaAs.
It flows from the substrate 1 toward the P-type cladding 1f43. This kind of phenomenon is caused by electrons in the active layer header Z at the time of high injection.
Even if the current overflows over the barrier (so-called gear leakage cage) and flows into the diversion stop layer 2, a multiplication effect of the transistor 9 occurs, and current flows from the P-type (1aAs substrate 1 to the P-type cladding layer). These currents are leakage currents that flow without passing through the main light emitting region, and have adverse effects such as deformation of the transverse mode or saturation of the optical output. The purpose of the present invention is to eliminate the above-mentioned leakage current, and to avoid the leakage current as described above. Half 3 with big output! Our mission is to embody and provide the...

In the semiconductor laser of the present invention, the semiconductor substrate formed on the P-type semiconductor substrate also has a large forbidden band width.
＋;'! , = a current blocking layer comprising at least an H conductor layer;
a striped groove in which the '11C flow blocking layer is absent (1), a P-type cladding layer formed on the striped groove and the current blocking layer, an active layer formed on the P-type cladding layer,
The N-type cladding layer formed on the active layer is
A region of the active layer above the striped groove is configured to be a main light emitting region.

The semiconductor laser according to the first embodiment of the present invention will be explained with reference to FIG. 1. Most of the first embodiment will be explained below! :'Same as VSIS laser, but current blocking layer 2 is pJ, U a A
The difference is that it is N, In,', Ga6.7F instead of s.

Since the current blocking layer 2 is made of Inl,jGa,5P, the forbidden band width is larger than that of GaAs. Therefore, in the transistor 9, the P-type GaAs substrate 1 and the current blocking layer 2 are
During this period, a barrier to holes is formed, and the emitter injection efficiency of the transistor 9 becomes extremely low. Therefore, the gain of the transistor 9 becomes extremely small. Therefore, even if, for example, electrons overflowing from the active layer 4 are injected into the current blocking layer 2, the gain of the transistor 9 is sufficiently small, so there is no multiplication effect and no large leakage current flows.

Moreover, since the ff1t flow blocking layer 2 is transparent to the Raded oscillation light at 7·j, it does not generate a photocurrent, resulting in leakage 71? , has the advantage of no flow.

In this embodiment, the current blocking layer 2 is N-type A1, 4Ga1
It may also be configured with 1'AS. In that case as well, the same effect as described in 6 above can be obtained.

Next, a method for manufacturing the semiconductor laser of this example will be described. No separation, l) type (laAs substrate l-hi) N type I n 5
．． t; Da Oaa, tlj flow prevention j consisting of y As
-2 to crystal growth. Growth method is 1□P one method, MBE
Any method such as method or MO-CVD method may be used. Next, striped grooves 8 are formed by photoetching. Next, a second crystal growth is performed to form a P-type cladding layer 3 and an active layer 4.
, the n-type 4171 layer 5 is sequentially and continuously grown. Form P812 electrode 6 and n-type i[@<'l at the bottom and perform tPJ 11.1 t from the wafer-C
'/L formation' No. l'i'j property B Even if it grows separately from others, it is 6.

FIG. 3 shows a cross-sectional view of a semiconductor laser according to a second example of M11 of the present invention. In Fig. 3, 11 is ■) type (1aAs
Board, 12 is N type AI J4: (]n '6tAS
The first current blocking layer 13 is made of N-type ()a As, and the second current blocking layer 14 is made of P.AI '6. J Ga
5.7 P-type cladding layer made of As, 15 is Alb,
4' (active layer consisting of Ja6.yAs, 16
N 2L consisting of beam type AI, 40aj, ',, As
This is the Lycranod layer. The difference from the conventional VSIS laser is that it includes a first current blocking layer 12.

The first current blocking layer 12 is made of N-type Al, 5A (-1a As
, a J5 barrier to holes is generated at the i-mitter junction of the transistor 20, and the c-mitter injection efficiency is extremely reduced. Therefore, Tran 9, Star 20
The gain of 1 is very small. Therefore, if the scattered light of the laser oscillation is absorbed by the stopping layer 13, for example, the current corresponding to that absorption J flows, but it is By evening 20, it increases by 6, and without any hesitation, the big r, I+'r it ”
+lt flow does not occur. -1 at high injection,
Even if there is a leakage that bypasses the active layer, the current is small and the optical output is large.

In the second embodiment, the first current blocking layer 12 is made of N-type A
I l,,'4'(Ja',:6 Instead of A s, it is N-type U a As, and the 21st L flow Ill stop layer 13 is N-type (]aAs, 1.<N-type Ale,<0ao14
6 As h Rui or N type I n17. (Ja 2), I
It may also be P.

In this case, the transistor 200 has a barrier between the eleventh current blocking layer 12 corresponding to the pace of the transistor 20 and the second current blocking layer 13 for holes.
The base transportation efficiency will be drastically reduced. Therefore, the gain of transistor 20 becomes very small. Therefore, the effect of multiplying the leakage current of transistor 20 #1 is almost non-existent.

In the embodiments described above, AlGaAs is used for the active layer, but the active layer is not limited to this, and for example, InGaAsP is used.
1 type or InGaAsP type may be used. Also, flat

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional VSI8 laser and a semiconductor laser according to a first embodiment of the present invention. FIG. 2 is a sectional view of a semiconductor laser in which the active layer is separated in the first embodiment of the present invention. FIG. 3 is a sectional view of a semiconductor laser according to a second embodiment of the present invention. In FIG. 1, 1 is a P-type GaAs substrate, 2 is a current blocking layer, 3 is a P-type cladding layer, 4 is an active layer, 5 is an N-type cladding layer, 6
1 N type electrode, 7 P type electrodes, 8 groove, 9 transistor, 11 P type GaAs substrate, 12 first current blocking layer, 13 second current blocking layer, 141 P type cladding Layer 15e is an active layer, and 16 is an N-type rad layer I. Figure 1 Figure 2

Claims (1)

[Claims] a current blocking layer formed on a P-type semiconductor substrate and including at least an N-type semiconductor layer having a larger band gap than the semiconductor substrate; a striped groove in which the current blocking layer is missing;
P formed on the striped grooves and the current blocking layer.
a type cladding layer, an active layer formed on the P-type cladding layer, and an N-type cladding layer formed on the active layer, and a region of the active layer above the striped groove serves as a main light emitting region. A semiconductor laser characterized by: 1.