JPS6159791A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To provide a laser light exit region in a high concentration P type region and to obtain high output, by interposing an active layer of superlattice construction between clad layers having wider forbidden bands and by bending the joint area near the laser resonating surface. CONSTITUTION:A semi-insulating N type GaAs substrate 31 is provided with an active layer 33 of superlattice construction consisting of multiple semiconduc tor layers of 100Angstrom or less, with a first clad layer 32 and with a second clad layer 34. The active layer 33 has a narrower forbidden band than those of the layers 32 and 34. The P-N junction between a low concentration P type impurity diffusion region 36 and the substrate 31 is vertical to the surfaces 40 and 40' of a laser resonator, but bent near the surfaces 40 and 40'. According ly, a laser light exit region 43 is located in the high concentration P type region 35. The absorption of laser light energy hupsilon1 can be effectively prevented by regulating the band construction of the high concentration P type region.

Description

[Detailed Description of the Invention] [1. Field of Application of Togami] The present invention relates to the structure of a semiconductor laser, and relates to a band gear near the laser resonant surface capable of high-output operation, and a band gear whose prism corresponds to the wavelength of the laser beam. , wider than the
This invention relates to a semiconductor laser that has a so-called wind stripe structure and whose oscillation transverse mode can be controlled.

[Methods of staying in the US and problems]

A wind stripe laser is conventionally known as a semiconductor laser device capable of high output operation.

However, it is difficult to control the depth of diffusion and concentration, and it is not suitable for mass production. As another example, several methods have been proposed that utilize buried growth technology to form a buried windstripe structure in the vicinity of the laser resonant surface using a semiconductor layer with a wider band gear than the active layer during buried growth. However, embedded growth is quite difficult,
The drawback is that it lacks mass production.

[Purpose of the invention]

An object of the present invention is to solve the above problems.

The object of the present invention is to provide a semiconductor laser with high output and controlled oscillator mode with good mass productivity through a simple manufacturing process.

[Structure of the invention]

Now, in a so-called superlattice structure formed by repeating semiconductor layers with a thickness of 100A or less.

It is known that heat treatment disturbs the superlattice structure due to self-diffusion of constituent atoms. This means fGaAs-
The AjAs-based superlattice structure will be explained. Figure 1, 8
Figure 2 shows the band structure of the superlattice structure before and after heat treatment, where 11°21 is the conduction band, 12.22 is the forbidden band width, and 13.23 is the valence band.

First, to explain Figure 1, in such a band structure, both electrons and holes gather in a semiconductor layer with a narrow forbidden band width, so light emission corresponding to the energy LVl in Figure 1 occurs. Both electrons and holes do not collect in a wide semiconductor layer, so the energy h
The light emission corresponding to ν is almost never generated.

By the way, in the band structure after heat treatment, as shown in Figure 2, the superlattice structure is not averaged out], and the energy of the forbidden band width hy3 is generally hν1 - hν, h''2
It is.

Now, since 11ν1<hν3, the light of energy hνl emitted from the first superlattice structure is this #! The band structure shown in Figure 2 does not absorb any absorption, which means that the band structure shown in Figure 2 has a thickness of 10
The same problem occurs whether the number of semiconductor layers of 0A or less is one layer or multiple layers.

Furthermore, it is known that this disorder of the superlattice structure is promoted by the diffusion of Zn.

The present invention takes advantage of the above phenomenon. That is,
A semiconductor laser having a wind stripe structure can be obtained by forming a diffusion region in the direction of the striped laser oscillation region so that the forbidden band width becomes wider near the laser resonant surface.

Furthermore, if the refractive index of the laser oscillation region (t) is made larger than the refractive index of the surrounding area of the laser oscillation region, it is possible to control a single oscillation transverse mode. Regarding the control of the oscillation transverse mode in the direction perpendicular to the substrate surface, 1.As is generally known, the wider the forbidden band width, the smaller the refractive index. On the other hand, the horizontal transverse mode can be controlled by utilizing the following phenomenon. The refractive index of the L5 superlattice structure in the at diagram is.

Since the thickness of each semiconductor layer in the superlattice is much thinner, hνl
A semiconductor layer having a forbidden band width of hν: and a forbidden band fr′ of hν:
It is the same as the average value of the refractive index of the semiconductor layer having x. Therefore, if there is no change in carrier immersion, the refractive indexes of the semiconductors in FIGS. 1 and 2 for light with energy hy1 are almost the same. By the way, it is known that when the carrier concentration is increased, the refractive index decreases by several orders of magnitude. Therefore, it is possible to control the horizontal transverse mode by making the carrier concentration in the laser oscillation region lower by υ than the peripheral portion of the laser oscillation region.

By utilizing the above phenomena in combination, it is possible to create a semiconductor laser with a windstripe structure in which the oscillation transverse mode is controlled. Moreover, whereas conventional semiconductor lasers with a wind stripe structure effectively realize differences in the forbidden band width by using impurity levels that are the same in the forbidden band, in the semiconductor laser of the present invention, the forbidden band width itself is changed. This makes it possible to realize a large difference in forbidden band width. Therefore, the semiconductor laser of the present invention can be expected to have a greater wind effect than a wind stripe laser having a conventional structure.

〔Example〕

An embodiment of the present invention will be described in full detail below with reference to the drawings. FIG. 3 shows the structure of the semiconductor laser of the present invention. In the MI diagram, 31 is a semi-insulating N-type GaAs substrate, 32 is a G
a 1-x A J xA a (0<x<13
The first cladding layer 33 is an active layer with a superlattice structure formed of multilayer semiconductor layers of 100A or less, and in this example, N-type Ga nyAJ, As-N-type Ga
AJ person (Okuy<z<x<1) Layer repetition 1
-ZZS and Cy is adjusted according to the oscillation wavelength.

34 is similarly Ga 1- zlAJ X/ As (
A second cladding layer consisting of a layer Q'-y-<z(x' (1), and the forbidden band of the active Nj33 is narrower than the forbidden band width of the second cladding layer 32.3; It has become.

Further, 35 is a high concentration P type impurity diffusion region (hereinafter referred to as high concentration P region) formed by Zn diffusion.

36 is a low concentration impurity diffusion region (hereinafter referred to as low concentration P region) formed by Zn diffusion, 37 is an N region, 38 and 39 are P-formed N electrodes, 40.40' is a pair of laser resonator surfaces, 41 is a Pn junction surface perpendicular to this laser resonator surface, 42.42' is a bent Pn junction surface near the laser resonator surface 40.40', and the width W of the bent portion is approximately 5μ and the protrusion length is X is approximately 15 μm, and 43 is the laser cavity surface 4.
This is the laser beam emission area at 0.

However, the characteristics of the semiconductor laser according to this invention are as follows.
As is clear from the above embodiment, the active layer 33 has a superlattice structure consisting of 100A repeating semiconductor layers, and the laser cavity surface 40.40' from which laser light is emitted is
The nearby p@joining surface 42°42' is bent, and this bending causes the laser light emitting region 43 on the cavity surface to become a high concentration P region.

First, it will be shown that a wind stripe structure is realized in semiconductor lasers formed in one or more ways. As mentioned above, disorder of the superlattice structure is promoted by Zn diffusion, so by using Zn as a P-type impurity,
The high concentration P region can have a hand structure as shown in FIG. 2, and the low concentration P region can have a band structure as shown in FIG.

That is, the laser beam emitting region 43 on the laser resonator surface 40, 40' is a high concentration P region.
When the laser oscillates and the energy of the nine beams is hv1, no absorption occurs near the laser resonator surface 40,40'. In other words, a wind stripe structure capable of high output operation has been realized.

Next, it will be shown that in the semiconductor laser of the present invention formed as described above, the oscillation transverse mode is controlled.

the active layer 33 than the first and second cladding layers 32,34;
Since the forbidden band width is narrower in 1. gz cladding layer 3
The active layer 33 has a higher refractive index than 2.34, which indicates that the vertical transverse mode can be controlled. Furthermore, the refractive index of GaAJ decreases as the carrier concentration increases.

Taking advantage of this fact, it is possible to control the horizontal and transverse modes. Figure 4 shows P in the active layer of the semiconductor laser of the present invention.
The carrier concentration determined by the diffusion profile in the direction across the n-junction 41 is shown, and FIG. Recognize. By the way, high concentration P
The carrier concentration in the region is 2 x 1019/c rn 3
The carrier concentration in the low concentration P region is 2×10 7c
This indicates the degree to which the current can be narrowed to the zero-order laser oscillation region, which is preferably less than m. 1st. Built-in potential φ1 of the P junction in the second cladding layer. Comparing the built-in potentiometer φ of the P junction in the active layer and the built-in potentiometer φ of the P junction in the active layer, it is found that the difference is due to the size of the forbidden band width.

φ, 〉φa, φ2〉φ8. Therefore, when a current is passed in the layer direction, the current flows across the Pn junction surface of the active layer. In other words, electrons and holes are at low concentration P in the active layer.
Light is injected into the active layer, and light emission occurs due to recombination.For the above reasons, in the low concentration P region of the active layer, light is confined due to the difference in refractive index, and light emission and recombination occur due to the injection of electrons and holes. It is possible to control laser oscillation and oscillation transverse mode.

As described above, according to the present invention, it is possible to easily realize a high-output laser with a controlled transverse mode using the commonly used method of 2 diffusion.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams showing the band structure of the superlattice structure before and after heat treatment, respectively. FIG. 3 is a diagram showing the structure of the semiconductor laser of the present invention. FIG. 4B is a diagram showing the carrier density distribution determined by the diffusion profile in the direction across the Pn junction in the active layer, and FIG. 4B is a diagram showing the refractive index distribution corresponding to the carrier density. 11, 12.13 respectively indicate the conduction band, forbidden band and single valence band in the band structure of the superlattice structure before heat treatment, 21,
22 and 23 respectively indicate the conduction band, forbidden band, and valence band in the band structure of the superlattice structure after heat treatment. 31... Semi-insulating N-type GaAs substrate, 3
2...First cladding layer (Ga, -xAJxA
sNl), 33...-=-active layer having a superlattice structure (
Ga, -, AJ, As-Ga1-2AIAa layer), 34
...Second cladding layer (G!11-x!AJx
lAs layer), 35...High concentration P type impurity diffusion region, 36...Low concentration P type impurity diffusion region, 37
......N shadow area, 38.39...P, N
Electrode, 40°40'... Laser cavity surface, 41
...Pn junction perpendicular to the laser cavity surface, 42.
42'...Bent P near the laser co-agulator surface
Junction surface, 43...and one light output area. A, -11 □21 □23 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] comprising first, second, and third semiconductor layers of a first conductivity type;
The semiconductor layer is formed of a multilayer superlattice structure formed by repeating layers with a thickness of 100 Å or less, and the forbidden band width of the semiconductor layer of the superlattice structure is equal to the bandgap width of the first and third semiconductor layers. A second conductivity type impurity is diffused into a narrower semiconductor substrate to form a high concentration second conductivity type impurity diffusion region and a low concentration second conductivity type impurity diffusion region in the first, second, and third semiconductor layers. In a semiconductor laser having a structure in which regions are respectively formed, a junction surface between the low concentration second conductivity type impurity diffusion region and the first conductivity type region is bent toward a side away from a laser waveguide in the vicinity of a laser resonance surface. In addition, a semiconductor laser device characterized in that a region where the extension of the waveguide and the laser resonant surface are in contact is a highly concentrated second conductivity type impurity diffusion region, and Z_n is used as the second conductivity type impurity.