JPS6037191A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To make an active layer near the end of a resonator thinner improving the maximum laser beams outputted by a method wherein, in an AlGaAs base CSP, both sides near the end of a resonator of a striped groove formed on a substrate are dented. CONSTITUTION:Both sides of a striped groove 10 on an N type GaAs substrate 1 are dented and an N type AlGaAs clad layer 2, an undoped AlGaAs active layer 3, a P type AlGaAs clad layer 4, an N type GaAs cap layer 5 are formed while a P type selective diffusion region 6 is provided and a P type and N type electrodes 13, 14 are formed. The laser beam output density of the active layer 3 at the end of the resonator may be reduced to restrain the temperature from rising up improving the maximum laser beams because the clad layer 2 at the dents 11 in the part B near the end is grown outstandingly and the thickness of the active layer 3 is reduced than that inside A of the resonator due to difference in growing speed while the peak position of field intensity distribution 9 in the vertical direction of oscillating beams is separated from the active layer 3.

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a high-power semiconductor laser.

Semiconductor lasers are used for optical fiber communication and information 4'+i%
g! It has been developed as a light source for In particular, as light sources for information processing such as optical disk writing or laser printers, AlGaAs visible light semiconductor lasers using GaAS substrates are currently the mainstream, and attempts are being made to increase the output in the fundamental line mode.

Among such Al0aAs-based visible light semicircular lasers, a channeled substrate planar stripe structure semiconductor laser (hereinafter abbreviated as C3Pv laser), which has a double heterostructure formed on a grooved GaAs substrate, has been proposed. has been done.

Figure 1 shows the cross-sectional structure perpendicular to the resonator of the above AlGaAs-based C8P v-zer, in which a striped groove 10 with a depth of 1 μm and 115 μm parallel to the (011) direction is installed on an n-type 0aAs substrate. On the (100) plane of l, a layer thickness of 0.3 μm outside of @1o is nm, AI
zAs first cladding layer (x~0.45) 2, layer thickness 0
．． 07 μill of undoped AlyGa, -y 3 oily layer (Y ~0.15) 3 2 μm thick p-type Alx
A four-layer structure consisting of a double heterostructure consisting of a Ga1 zAs second cladding layer 4 and an n-type GaAs cap layer 5 positioned above the pmAtXaa1-XAs second cladding layer 4 is one continuous liquid phase growth process. A flat Alv (ElyAs active layer) is obtained even on the groove 10. Also, a stripe with a width of 7 μm for current confinement is formed along the ζ10 in the above 1), and a p-type bush and an n-type Ohmic metalworks 3 and 14 are provided.

CS with 1) Laser has the advantage that it can be manufactured more easily than one-time liquid phase growth IC.

In the above C8P laser, the tail of the vertical light distribution centered on the active layer reaches outside the groove (till) inside the substrate, giving an effective Jli index difference between the inside and outside of the groove.
Light is confined within the width of the groove, and the fundamental transverse mode can be detected with a relatively low threshold current of 50 to 60 mA.

By the way, the general Ic AI 0aAs system visible laser is as follows.

When the active layer at the cavity edge absorbs light,
In order to raise the starting level of optical damage and improve the maximum optical output, while having the disadvantage that the maximum optical output is limited due to the optical damage phenomenon in which the end face is melted and destroyed due to a sudden increase in temperature expansion. K is generally the resonator end face -C
There are two methods: one to reduce the original absorption coefficient, and the other to reduce the optical output vM degree at the end face of the active region.

Conventionally, in the C8P laser described above, the active layer is formed as thin as 0.07 μm over the entire cavity length, and the electric field distribution of the oscillated light is improved by increasing the seepage of light into the upper and lower cladding layers that sandwich the active layer. By spreading in the direction perpendicular to the active layer, the optical output density at the end face of the active layer is reduced, the optical damage initiation level is raised, and the optical output is improved. However, this optical output is about 15 to 20 mW at maximum, and 20 mW.
This was insufficient as a light source for writing on optical discs or for laser printers, which require a first output of mW or more.

The object of the present invention U5 is to provide a method for manufacturing a semiconductor laser having a structure that further improves the maximum optical output of the C8P laser.

According to the present invention, by providing depressions on both sides 1 of the groove in the vicinity of the end face of the resonator of the semiconductor substrate in which a uniform IR is formed over the entire length of the resonator, the part of the beach sandwiched between the depressions on both sides Since the thickness of the first cladding layer and active layer of the double-hetero I:+s structure can be made thinner than that inside the resonator, the height of the active layer relative to the substrate surface is smaller near the end face of the resonator than inside the resonator. low, the layer fV of the active layer,
i1 The above-mentioned force 11 < The active layer is thinner near the end face of the resonator than inside the resonator, and the active layer extends over the entire length of the resonator and is flat J4j in the direction perpendicular to the groove near the top 15 of the groove. , C which combines a double hetep structure with an active layer as an intermediate layer
An 8P laser structure is realized. As a result, firstly, the active layer near the end face is moved away from the peak position of the light distribution in the vertical direction of the oscillated light, reducing the optical output v 4 at the active layer end face, and secondly, the active layer near the end face is moved away from the peak position of the light distribution in the vertical direction of the oscillation light. By making the beam thinner and reducing the amount of light absorbed, it is possible to suppress the optical damage caused by the temperature rise at the end face of the resonator, and (1) significantly increase the maximum optical output.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The Puno method for manufacturing a semiconductor laser according to the present invention will be described below with reference to the drawings.

FIG. 2 shows an enlarged view of the n-type GaAS substrate 1 according to the present invention.
A recess 11 with a width of 20 to 30 μm and a depth of 1 μm is formed in the direction perpendicular to the groove 10 from a position approximately 5 μIn away from the groove 10 on both sides at t7? It was formed by a photoresist method at the same time as 1□.

FIG. 3 is a cross-sectional view perpendicular to the groove direction in the vicinity of the end face B of an element with a multilayer structure formed in the subsequent manufacturing process, and is similar to that described in FIG. 1 on the n-type GaAs substrate l. n-type AlXG by one continuous oil phase growth under the growth conditions of
a, -XAs first layer, de layer 2, undoped AlyGa
1 yAs active layer 3, p translationl 1xGa,.

A, 9 second cladding layer 4 and n-type GaAs capping layer 5 are sequentially formed, and Z
A pm selective diffusion region is provided by n diffusion, and then p-type and n-type ohmic electrodes 13 and warps 14 are formed on the front and back surfaces of this wafer.

In the liquid phase growth process, the growth of the n-type Alx0at-xAS cladding layer 2 in the recesses 11 on both sides becomes dominant in the vicinity of the end face I3, and the growth of the n-type Alx0at-xAS cladding layer 2 in the recesses 11 on both sides becomes dominant. The above n-type A at the top of the two mesas 12 warped grooves lO]
The growth rate of the xGa, -xA5 layer 2 decreases, and the layer 2 is formed, which has a flat surface but is about 0.15 μm thinner than that of the resonator. A difference occurs between the inside A of the resonator and the area B near the two upper end faces of the resonance. Similarly, the layer thickness of the active layer 3 on the n-type Atxo, 1xAs clad layer 2 is also 0 in the resonator interior A due to the difference in growth rate.
．． B′t′FJ near the resonator end face is 0.0 compared to 0.07 μm.
4 μm means that the pressure decreases by approximately half.

FIG. 4 shows a semiconductor laser t according to the present invention described in FIG.
l - Viewed from the side, the round groove bottom 8 formed on the substrate surface 7
The height and layer thickness of the active layer 3 above γR10 are approximately 0 at B near the cavity end face compared to A inside the cavity. .15 μm and about 0.3 μm. 4 of oscillation light
i: The peak position of the electric field strength distribution 9 in the vertical direction coincides with the position of the active layer A′t″1″ inside the resonator, whereas
In the vicinity of the end bend B, the active layer is approximately 0.15 μm away from the peak position of the electric field intensity distribution 9, so the optical output density of the active layer 3 at the resonator end face is reduced to less than half compared to the conventional one. In combination with the effect of reducing the amount of light absorbed by the thinner layer 11 of the active layer 3 at the resonator end face, the temperature rise at the resonator end face can be suppressed to less than half.

As a result, the threshold current is about the same as that of the conventional C8P laser, but the maximum optical output ij is increased to 40 mW or more, which is more than double.

As described above, according to the present invention, AIGQAs-based C8P
In the laser, by adding depressions to both sides of the striped grooves formed in the G, A, and substrate near the cavity end face, the height of the active layer is lower near the cavity end face than inside the cavity. , the active layer deviates from the peak position of the oscillation light, and the active layer becomes thinner, which reduces the optical output density and the amount of absorption in the active layer at the end face, making the maximum optical output more than double compared to the conventional one. It becomes possible to do so.

At this time, the striped groove is uniform over the entire length of the resonator, and the active layer formed thereon is flat in the direction perpendicular to the resonator near the top of the groove, resulting in poor reproducibility. 6, which is preferable in this point, yet other laser characteristics such as threshold current remain unchanged.

Furthermore, even if the A1 composition of the &'cp type, n22, and de layers is different, or the conductivity type of the upper n11 is changed, or AlGaA
It goes without saying that the present invention is also applicable to the case of using a semiconductor substrate which is limited to s-based light and has a high absorption of light.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a conventional semiconductor laser cavity, and FIGS. 2, 3, and 4 are schematic diagrams of each manufacturing process of the semiconductor laser according to the present invention. A sketch of the substrate, FIG. 3 is a 11m view perpendicular to the resonator near the end face of the resonator, and No. 41 is a cross-sectional view in the direction of the resonator. In the figure, common numbers represent common names. 1, nm, ('1aAs 5 plates, 2.n-type Alx (
jaI XA8 1st class, do layer, 3. Al, Ga,
, As activation, 4゜p i AI X Ga 1 zA
s second cladding layer, S n-type Ga AS cap layer, 6. ρ type selective diffusion region, 7°n type G, groove outer surface of As substrate (dashed line), 8. Groove bottom of n-type GaAs substrate, 9. Vertical electric field intensity distribution of oscillated light, 10.0 type GaA, striped grooves on substrate, 11. n-type GaA
, board bending, l 2. Substrate mesa 8i1 near the resonator end face. I 3. p-type ohmic electrode, 14,
N-star ohmic electrode, A, inside the resonator, B, near the end face of the resonator. Representative Patent Attorney Uchihara Figure 1 Figure 2 0

Claims (1)

[Claims] ! a first step of providing, on a first semiconductor substrate having a first conductivity type, a striped groove and a recess located near the end face of the pair of loss devices on both sides of the striped groove;
a second semiconductor layer having a first conductivity type and a larger forbidden band width than the first semiconductor substrate; a second semiconductor layer on the second semiconductor layer; a fourth semiconductor cladding layer having a third cylindrical shape having a bandgap smaller than that of the semiconductor cladding layer; and a fifth semiconductor having a first conductivity type on the fourth semiconductor cladding layer. In the second step of epitaxially/dialically growing the cap layer and the cap layer, a fourth semiconductor cap layer having the second conductivity type is added to the fifth semiconductor cap layer directly above the striped groove. The third step is to selectively form striped impurity expansion fA't, i$ reaching the layer, and the second conductivity type ohmic, RL pole, on the surface of the 50th semiconductor V cap. a fourth step of forming an ohmic electrode of the first conductivity type on the M-plane of the first semiconductor substrate; 1. A method for manufacturing a semiconductor laser, characterized in that the number of kings of 5 and 1 is 7, which forms a wide open plane and isolates elements between adjacent stripes.