JPH01175284A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To make a laser element oscillate stably for a long period even though it oscillates with a high beam output, by laminating a p-type optical absorption layer having an energy gap smaller than that of an active layer, a p-type carrier block layer having an energy gap larger than that of the optical absorption layer, and an n-type electric current bottleneck layer in order on one side of clad layers so that each stripe region is sandwiched between the above layers. CONSTITUTION:An n-type clad layer 22, a p-type active layer 23, a p-type clad layer 24, a p-type optical absorption layer 25, a p-type carrier block layer 26, an n-type electric current bottleneck layer 27, and an n-type layer 28 are laminated in order. Then, a photoresist mask is formed in a stripe like pattern and the current bottleneck layer 27 is etched halfway and continuously is etched by HF. Further, the p-type optical absorption layer 25 is etched by an etchant consisting of NH4OH and H2O2. In this way, after forming a groove part 20 having a cross section form of an inverted trapezoid, the photoresist mask is removed. A p-type clad layer 29 is laminated on the n-type GaAs layer 28 and in the groove part 20 by an ordinary liquid phase epitaxy process. Then, a p-type cap layer 30 is laminated and an electrode is mounted on its layer. Thus, there is no possibility that the temperature in the active layer rises, and this approach prevents the deterioration of the element even though this element oscillates with a high light output and then, the element oscillates stably for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor laser device that stably oscillates in a single mode up to high output.

(Prior Art) A semiconductor laser element capable of oscillating coherent light is used as a light source of an optical disk device.

Among optical disk devices, rewritable optical disk devices that are capable of writing and erasing information have also been developed. The semiconductor laser element used in the optical pickup light source of such a rewritable optical disk device only needs to oscillate at a low optical output of about 31 m when reading a signal, but when writing or erasing a signal it oscillates at a high optical output of about 30 m - or more. It is necessary to oscillate at the output.

For this reason, the current-light output characteristic (I'-L characteristic) of such a semiconductor laser element for a light source can vary linearly so that it can oscillate stably from low optical output to high optical output. It becomes necessary.

The conventional VSIS (V-grooved 5ubs) exhibits very good characteristics as a low-power semiconductor laser device.
ratedInner 5tripe) The structure of the laser device is shown in FIG.

The laser device is manufactured in a first-order manner. first.

A current confinement layer 32 is laminated on a substrate 31 . Next, a groove having a V-shaped cross section is formed in the center of the current narrowing VN 32 so that its bottom reaches the substrate 31, and a cladding layer 33 is laminated inside the groove and on the current narrowing layer 32. Then, an active layer 34 is formed on the cladding layer 33. A cladding layer 35 and a cap layer 36 are sequentially laminated. This allows VSIS
A laser is manufactured.

(Problem that the invention attempts to solve) A VSIS type semiconductor laser device having such a structure is as follows.

The energy gap of the current confinement layer 32 existing on each side of the V-shaped groove in cross section is smaller than the energy gap of the active layer 34 disposed above the active layer 34 where light is oscillated, and the active layer 34 oscillates light. The light leaking through the cladding layer 33 is absorbed by the current confinement 1J32, thereby stabilizing the optical oscillation mode.

The current confinement layer 32 becomes a p-type when the substrate 31 is an n-type, but in this case, electrons, which are minority carriers generated by light absorption in the current confinement layer 32, are quickly released from the current confinement layer 32. As a result, the holes, which are majority carriers, remaining in the current confinement layer 32 are accumulated, and the energy barrier is lowered. As a result, in order to oscillate at high output, there is a drawback that the current confinement layer 32 must be thickened to several μm or more to increase the energy barrier.

On the other hand, if the substrate 31 is p-type, the current confinement layer 32 is n-type. In this case, in the current confinement layer 32, the diffusion of holes, which are minority carriers, generated by light absorption is quickly suppressed by increasing the concentration of electrons, which are majority carriers, in the current confinement layer 132, and the current In the constriction layer 32, there is a high possibility that non-radiative recombination of electron-hole pairs will occur,
Almost no accumulation of majority carriers occurs. the result,
Even if the current confinement layer 32 is as thin as 1 μm or less, current confinement is still possible. However, it has been found that in such an n-type current confinement 132, in addition to non-radiative recombination, holes also combine with phonons to increase the temperature.

In particular, the temperature rises significantly around the V-shaped cross-sectional groove that is the light emitting part, so please be careful when oscillating at high output.

This temperature-rising portion deteriorates, and there is a drawback that it is not possible to oscillate stably at high output over a long period of time.

In this way, in conventional semiconductor laser devices, the current confinement layer has a smaller energy gap than the active layer, so regardless of whether the current confinement layer is n-type or p-type, it is stable at high output over a long period of time. The problem is that it is not possible to cause optical oscillation.

The present invention solves the above-mentioned conventional problems.

The purpose is to provide a semiconductor laser device that can stably oscillate over a long period of time up to a high optical output.

(Means for Solving the Problems) The semiconductor laser device of the present invention is a semiconductor laser device having an active layer sandwiched between a pair of cladding layers, which absorbs p-type light and has a smaller energy gap than the active layer. layer and
a p-type carrier block layer having a larger energy gap than the light absorption layer;

an n-type current confinement layer on one side of the cladding layer.

The above-mentioned object is achieved by sequentially stacking layers with striped regions forming current paths extending in the resonance direction sandwiched therebetween.

(Example) The present invention will be described below with reference to Examples.

For example, as shown in FIG. 1, the semiconductor laser device of the present invention has a p-type GaAs substrate 11 and an n-type Gao, 7°.Alo, zsAs current confinement N12. p-type Gao,
25'AI0. ? A 58S carrier block layer 13 and a p-type GaAs light absorption layer 14 are laminated. At the center of the upper surface of the light absorption layer 14.

Carrier block layer 13. Through the current constriction 112.

A groove 19 having a 7-shaped cross section and whose bottom reaches the top of the substrate 11 is formed in a striped shape. Inside the groove and on the light absorption layer 14, p-type Gao, s, Alo, 43AS
Clad JEJ15 is laminated. The cladding layer 1
5 has a flat top surface. The cladding layer 15 includes:
p-type Ga6.5sA1o, +sAs active layer 16. n-type Ga6. S7 eight 10.43 eight S cladding layer 17. n-type G
AAs cap layers 18 are sequentially laminated. Further, electrodes (not shown) are provided on the cap IJ18 and the substrate 11, respectively.

Gao layered on the p-type substrate 11, 75A]o,
The 2SAS current confinement layer 12 is of n-type, which is a conductivity type opposite to that of the substrate 11. In addition, Ga is in contact with one cladding layer 15 of a pair of cladding layers 15 and 17 sandwiching the active layer 16, leaving a V-shaped groove 19 of a predetermined width extending in the resonance direction.
The As light absorption layer 14 is p-type and has a small energy gap because AI is not mixed crystal. Ga laminated between the light absorption layer 14 and the current confinement layer 12
SAl. ,,.

The As carrier block layer 13 is also p-type.

The A1 composition ratio is large, and therefore the energy gap is larger than that of the light absorption [14]. Furthermore, each Gao, 57
A1. ．． 4. The IAs cladding layers 15 and 17 have a thicker A1 composition ratio than the active layer 16 (therefore, the active J'
The energy gap is larger than i16.

The semiconductor laser device of the present invention has such a configuration.

For example, it is manufactured as follows. First, current confinement layers 12 are formed on a p-type G5As substrate 11 to form n-type Gao, tsAlo, and zs8 layers. p-type Gao, to zs8. , , As carrier block layer 13. Two p-type GaAs light absorption layers 14 are sequentially laminated by a conventional liquid phase epitaxial (LPE) method. Thereafter, a photoresist is formed using a normal photolithography method so that a striped pattern extending in the resonance direction and having a dimension of about 3 μm in the width direction remains at the center in the width direction (direction perpendicular to the resonance direction). Next, using the photoresist as a mask, H2SO4 and 1120
Etching is performed using an etching solution containing a mixture of □ and l'bO in a ratio of 1:2:10 to form a groove 19 having a V-shaped cross section whose bottom reaches the substrate. After removing the photoresist, the inside of the groove 19 and the light absorption layer 1 are
p-type Gao on 4, S? An AI0.43AS cladding layer 15 is laminated by the LPE method, and the cladding layer 15
p-type Ga@0. , A1. , ,5As
Active layer 16. n-type Gao, S? Old. , 4JS clad N17. and an n-type GaAs cap layer 18 are sequentially laminated by the LPE method. Next, for example, the p-type substrate 11 is made of Au-Zn, and the n-type cap layer 18 is made of Au-Ge-N.
A semiconductor laser device of the present invention can be obtained by vapor-depositing i and forming each electrode.

In the semiconductor laser device of the present invention, the current is confined in the current confinement layer 12 and the striped groove 19 serves as a current path, so that the inner portion of the active layer 16 facing the opening of the V-shaped groove 19 is Light is oscillated.

The light oscillated within the active layer 16 is transmitted to the portion of the active layer 16 facing the thin cladding layer 15 excluding the square groove portion 19.

The light passes through the cladding layer 15 and is absorbed by the light absorption N14 whose energy gap is smaller than that of the active layer 16.

As a result, the refractive index of the active layer 16 changes equivalently in the horizontal direction, and the region within the active layer 16 facing the square-shaped groove portion 19 and the region within the active layer 16 other than that are as follows.
The effective refractive index is different, and the light oscillated in the active layer 16 is
The light beam is confined within the optical waveguide formed in the region facing the letter 2-shaped groove, and propagates stably.

Since the light absorbing Jti14 is p-type, the minority carriers generated by light absorption are electrons and have a long diffusion length.

Since the carrier block layer 13 having a larger energy gap than the light absorption layer 14 is interposed between the light absorption layer 14 and the current confinement layer 12, electrons, which are minority carriers, generated in the light absorption layer 14 is not injected into the current confinement layer 12, and a reverse bias between the current confinement layer 12 and the substrate 11 can be maintained. on the other hand.

Minority carriers generated by light absorption in the light absorption layer quickly diffuse, thereby preventing a concentrated temperature rise in the vicinity of the part where light is oscillated.

FIG. 2 is a sectional view of another embodiment of the semiconductor laser device of the present invention. The semiconductor laser device includes an n-type GaAs substrate 2
n-type Gao on 1, 57A10. a3As cladding layer 22° p-type Gao, asAlo, Is8 to active layer 23. P-type Gao, s, ^10.4'J8S cladding layers 24 are sequentially laminated. On each side in the width direction of the cladding layer 24, a p-type GaAs light absorption layer 25°p-type GaO,
zsAl o, 7Js carrier block layer 26. n
A Gao, tsAlo, and tsAs current confinement layer 27 and an n-type GaAs layer 28 are sequentially laminated, and a striped groove 20 having an inverted trapezoidal shape and extending in the resonance direction is formed in the widthwise center of the cladding layer 24. There is. The n-type Ga
On the As layer 28 and in the trench, p-type Ga6. s7^1
゜、４． An As cladding layer 29 is laminated, and the upper surface of the cladding layer 29 is flat. A p-type GaAs cap layer 30 is laminated on the cladding layer 24.

In the semiconductor laser device in this example, the cladding layer 2
4, the p-type GaAs light absorption layer 25 is laminated with a groove region of a predetermined width extending in the resonance direction.
asAl. , , the energy gap is smaller than that of the 5As active layer 23, and the p layer laminated on the light absorption layer 25
The carrier block layer 26 is of type Ga, zsAla, tsAs.

Since the At composition ratio is large, the energy gap is larger than that of the light absorption layer 25. n-type gas on the carrier block layer 26, 7581. , HAs current confinement layers 27 are stacked.

A semiconductor laser device having such a configuration is manufactured as follows. First, on the n-type GaAs substrate 21, an n-type GaAs
, S? AI+1. asAs clad Ff22.
p-type Gao, 55AIo, +5As active layer 23.
p-type Gao, 5J1o, 43AS cladding layer 24.
p-type GaAs light absorption layer 25. p-type Gao, zsAIo
, vJ! Carrier layer 26. n-type Ga...
? SA1+1. zsAs current confinement N27゜n-type GaA
Two s-layers 28 are sequentially laminated by a conventional metal organic chemical vapor deposition method (MOCVD method). Next, a photoresist mask is formed using a conventional photolithography method so that a striped pattern having a width of 4 μm and extending in the resonance direction remains at the center of the two width directions.

After that, the part of the striped pattern other than the mask is treated with a mixture ratio of +1□SO, Hgo□ and H2O of 1.
: With an etching solution of 2:10, ・Current confinement layer 2
Etch halfway through step 7, then continue etching with HP (hydrofluoric acid). Since IP does not etch the GaAs layer, the p-type GaAs light absorption layer 25 is not etched. Furthermore, p-type GaAs was etched using an etching solution with a mixing ratio of NH4OH and H2O of 1:20.
The light absorption layer 25 is etched. This etching liquid.

It is not possible to etch a layer with a high mixed crystal percentage of AI,
The p-type Gao, 5JIo, 43AS cladding layer 24 is not etched.

After forming the groove portion 20 having an inverted trapezoidal cross-section in this manner, the photoresist mask formed on the n-type GaAs layer 28 is removed, and a normal liquid phase growth method is used.

p-type Ga6. S? An AI6.4zAs cladding layer 29 is laminated on the n-type GaAs layer 28 and in the trench 20, and a p-type GaAs cap layer 30 is further layered on the cladding 129.
Laminate. Then, the cap layer 30 and the substrate 21
Place electrodes on.

The semiconductor laser device of this example is obtained by forming folds with a predetermined length in the resonance direction.

In the semiconductor laser device having such a configuration, the current is confined in the current confinement layer 27 as in the semiconductor laser device of the above embodiment, and the groove 20 becomes a current path, so that the active layer 23 facing the bottom of the groove 20 is confined. Light is emitted within the area. Then, part of the light passes through the thin cladding layer 24 on the active layer 23 and is absorbed by the light absorption layer 25, which has a smaller energy gap than the active layer 23. As a result, the refractive index of the active layer 23 changes isometrically in the horizontal direction, and the light oscillated within the active layer 23 is confined in the optical waveguide formed in the portion facing the bottom of the groove. Propagates stably.

Between the light absorption layer 25 and the current confinement layer 27, the light absorption layer 2
Since the carrier block layer 26 with a larger energy gap than that of 5 is interposed, the minority carriers generated in the light absorption layer 25 when the light absorption layer 25 absorbs light are electrons, and the diffusion length is long, but the active The current is not injected into the current confinement layer 27 which has a larger energy gap than the layer 25, and a reverse bias between the current confinement layer 27 and the p-type cladding layer 24 can be maintained.

In the above embodiment, a GaAlAs/GaAs semiconductor laser device was explained, but InP,
InP as current confinement layer, 1nGaAs as light absorption layer
The present invention can also be applied to InGaAsP/InP semiconductor laser devices using InGaAsP/InP.

(Effects of the Invention) In the semiconductor laser device of the present invention, the light absorption layer is disposed in such a way that it is in contact with one of the pair of cladding layers sandwiching the active layer, leaving a region of a predetermined width extending in the resonance direction. Therefore, an optical waveguide is formed within the active layer, and light stably propagates within the optical waveguide. Since the carrier blocking layer is interposed between the light absorption layer and the current confinement layer, minority carriers generated by light absorption in the light absorption layer are quickly diffused without being injected into the current confinement layer. There is no fear that the temperature will rise in the vicinity of the region of the active layer where light oscillation occurs. As a result, the semiconductor laser device of the present invention has no risk of deterioration even when oscillated at a high optical output, can stably oscillate up to a high optical output over a long period of time, and can be suitably used as a light source for an optical disk device.

FIG. 1 is a sectional view showing an example of the semiconductor laser device of the present invention, FIG. 2 is a sectional view showing another example of the semiconductor laser device of the present invention, and FIG. 3 is a sectional view of a conventional semiconductor laser device. FIG. 2 is a cross-sectional view showing an example of a laser.

11 = n-type GaAs substrate, 12-n-type Gao, 7
SAIQ, 2. AS current confinement layer, 13-p type Gao,
2SA10.758S carrier block layer, 14P
Type GaAs light absorption layer + 1s-p type Gao, 57Alo,
43AS cladding layer, 16-1 type Gao, esAl
o, +s8 to active layer, 17... n-type Gao, 57
AI0.43AS cladding layer, 18...n-type GaA
s cap layer, 19... groove portion, 20... groove portion, 21
...n-type GaAs substrate, 22-n-type Gao, 5J1
o, 4JS cladding layer, 23...p-type Gao, 1
sA1o, +sAs, 24- P-type Gao, to st8. , 438s cladding layer, 25... p-type GaAs light absorption layer, 26... p-type Gao, zsAlo, 7S
AS carrier block layer, 27... current confinement layer.

that's all

Claims (1)

[Claims] 1. A semiconductor laser device having an active layer sandwiched between a pair of cladding layers, a p-type light absorption layer having a smaller energy gap than the active layer, and a p-type carrier having a larger energy gap than the light absorption layer. A semiconductor laser device in which a block layer and an n-type current confinement layer are sequentially laminated on one side of the cladding layer with a stripe region serving as a current path extending in the resonance direction sandwiched therebetween.