JPH0613694A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To provide an AlGaInP semiconductor laser which allows high power operation with reduced temperature increase on the activating area edge plane. CONSTITUTION:A semiconductor laser is provided with an area which allows no current injection in the vicinity of a resonator edge plane. Namely, for the double hetero junction structure formed on a semiconductor substrate for the semiconductor laser composed of (AlxGa1-x)0.5In0.5P, at least an activating layer is sandwiched by a first clad layer of the first conductivity type and a stripe mesa shaped second clad layer of the second conductivity type. A semiconductor layer of the first conductivity type with a larger refraction factor than the activating layer is provided on the stripe mesa side and on the external part and a Ga0.5In0.5P layer of the second conductivity type is provided only on the stripe mesa top plane of the second clad layer excluding the vicinity of a resonator edge part. The area which allows no current injection is formed by removing the Ga0.5In0.5P layer of the second conductivity type in the vicinity of the resonator edge planes, heat in the vicinity of the edge plane is reduced when laser is oscillated and high power operation is allowed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser for a bar code reader such as a POS or FA system or a light source for a laser printer, and more particularly to a lateral mode control with high output. And a structure of an AlGaInP-based visible light semiconductor laser having an oscillation wavelength of 680 nm or less.

[0002]

2. Description of the Related Art Conventional lateral mode control type AlGaInP
An example of a visible light semiconductor laser is reported on page 165 of the proceedings of Autumn Society of Applied Physics, 1986.

The conventional semiconductor laser will be described with reference to FIGS. 3A and 3B. FIG. 3A shows a conventional lateral mode control type AlGaInP visible light semiconductor laser. 3B is a perspective view showing the structure of FIG. 3B, and FIG. 3B is a sectional view taken along the line EE of FIG. In FIGS. 3A and 3B, 1 is an n-GaAs substrate, and an n-GaAs buffer layer 2 is formed on this substrate 1. Then, n-AlGa is formed on the buffer layer 2.
InP clad layer 3, GaInP active layer 4, p-AlG
aInP clad layer 5, p-GaInP cap layer 6,
A double heterojunction structure composed of the n-GaAs current blocking layer 7 and the p-GaAs contact layer 8 is formed.

A crystal for a semiconductor laser having this structure is
Usually, it is manufactured by the MOVPE method, but it is technically difficult to stack an AlGaInP layer on a substrate having a step formed thereon. Therefore, as shown in FIG. 3A, the GaInP active layer 4 is formed on the GaInP active layer 4. By forming the p-AlGaInP clad layer 5 having a step and forming the n-GaAs current blocking layer 7 on the step, the current confinement and the optical waveguide action are performed in a self-aligned manner.

Here, the manufacturing process of the semiconductor laser having the conventional structure shown in FIGS. 3A and 3B will be briefly described. First, the n-GaAs buffer layer 2 is formed by the first MOVPE growth. A five-layer structure up to the p-GaInP cap layer 6 is sequentially formed. Subsequently, a stripe-shaped mask using a SiO ₂ film having a width of 5 μm is formed on the cap layer 6 by a photo-etching method, and the p-AlGaInP clad layer 5 is partially etched to form a stripe-shaped mesa portion. .

Then, by the second MOVPE growth, n-Ga is formed in the mesa portion excluding the stripe-shaped SiO ₂ film mask.
The As current blocking layer 7 is selectively formed. After that, Si
After removing the O ₂ film mask, the p-GaAs contact layer 8 is grown on the entire surface by the third MOVPE growth, and the p-side electrode 9 is formed on the contact layer 8 and the n-side electrode 10 is formed on the n-GaAs substrate 1. By doing so, the laser device having the structure shown in FIGS. 3 (a) and 3 (b) is completed.

In this structure, the current confinement is n-GaAs.
This is performed by the current blocking layer 7. In addition, p-GaInP
The cap layer 6 is formed of the p-AlGaInP cladding layer 5 and the p-layer.
It has a role to prevent the increase of electric resistance caused by the band discontinuity with the -GaAs contact layer 8 (for example, Proceedings of the Autumn Society of Applied Physics, 1987, P.765, lecture number 19).
a-ZR-6), and as shown in FIG. 3B, both end faces in the cavity direction are formed.

On the other hand, the lateral mode control is p-
On both sides of the mesa of the AlGaInP clad layer 5, n-Ga is formed.
Since light absorption loss occurs due to the As current blocking layer 7, this is performed by forming a refractive index distribution on both sides of the mesa.

[0009]

In recent years, there has been an increasing demand for an AlGaInP-based visible light semiconductor laser capable of oscillating in a basic lateral mode and realizing a high output operation. However,
In the conventional refractive index guide type semiconductor laser as described above,
Since the p-GaInP cap layer 6 is formed up to both end faces in the cavity direction (see FIG. 3), current injection raises the temperature in the active region (GaInP active layer 4), and further,
At the end surface of the active region, heat is generated because the laser light is absorbed by the end surface, the temperature of the end surface rises, optical damage easily occurs, the end surface destruction output decreases, and high output operation becomes difficult. Become.

The present invention solves such a problem and enables high output operation by reducing the temperature rise of the end face of the active region.
It is an object of the present invention to provide an lGaInP based semiconductor laser.

[0011]

The semiconductor laser of the present invention is provided with a current non-injection region in the vicinity of the end face of the resonator to reduce the temperature rise of the end face of the resonator due to the current injection and to increase the end face breakdown output. It enables high output operation.

That is, according to the present invention, the double heterojunction structure portion formed on the semiconductor substrate is (Al _x Ga _{1 -x} ) _0.5 In _0.5.
In a P-based semiconductor laser, at least the active layer is sandwiched by a first conductivity type first cladding layer and a second conductivity type stripe-shaped mesa-shaped second cladding layer, and the stripe-shaped mesa side. A second conductivity type Ga _0.5 In _0.5 P layer only on the upper surface of the stripe-shaped mesa of the second glad layer excluding the vicinity of the cavity end, and a semiconductor layer of the first conductivity type having a higher refractive index than the active layer. A semiconductor laser characterized by comprising:

[0013]

In the present invention, p-Ga is formed only in the vicinity of the cavity end face.
By removing the InP cap layer, the p
A band discontinuous junction is formed between the -AlGaInP clad layer and the p-GaAs contact layer, and the electrical resistance increases, so that the current non-injection region acts.

The width of this current non-injection region is at least 5
If it is μm, the effect of the present invention is not impaired, but it is preferably 10 μm.

[0015]

The present invention will be described in detail with reference to FIGS. 1 (a) to 1 (d) and FIGS. 2 (a) and 2 (b). 1 (a) to 1 (d) are views showing an embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are views showing another embodiment of the present invention.

(Embodiment 1) FIG. 1A is a perspective view showing the structure of a semiconductor laser according to an embodiment of the present invention.
(b), (c) and (d) are sectional views taken along the line AA shown in FIG. 1 (a), respectively.
FIG. 3 is a cross-sectional view taken along line B- and CC.

First, as a raw material, a metal group 3 organic metal (trimethylindium, triethylgallium, trimethylaluminum) and a group 5 hydride (PH ₃ , AsH ₃ )
By the MOVPE method under reduced pressure using and, n of the plane orientation (100)
-On a GaAs substrate 11 (n concentration 2 × 10 ¹⁸ cm ⁻³ ), a 0.5 μm thick n-GaAs buffer layer 12 (n concentration 1
X 10 ¹⁷ cm ^-3 ), and a thickness of 1 μm of n- (Al _0.6 G
a _0.4 ) _0.5 In _0.5 P clad layer 13 (n concentration 5 × 10 ¹⁷
cm ⁻³ ), 0.06 μm thick Ga _0.5 In _0.5 P active layer 1
4, p- (Al _0.6 Ga _0.4 ) _0.5 In _{0.5 with} a thickness of 1 μm
P clad layer 15 (p concentration 3 × 10 ¹⁷ cm ^-3 ), thickness 0.1
μm p-Ga _0.5 In _0.5 P cap layer 16 (p concentration 1
× 10 ¹⁸ cm ^-3 ) sequentially grown to double hetero wafer-
To form.

Subsequently, a rectangular SiO ₂ film having a width of 5 μm and a length of 280 μm is formed on the cap layer 16 by a photo-etching method. Then, using an HCl-based etching solution,
Only the p-Ga _0.5 In _0.5 P cap layer 16 except for the rectangular SiO ₂ film region having a width of 5 μm and a length of 280 μm is selectively removed by etching. Next, a stripe-shaped SiO ₂ film having a width of 5 μm is formed on the first rectangular SiO ₂ film by the second photo-etching method.

Therefore, as shown in FIGS. 1 (c) and 1 (d), p- (Al _0.6 G) is used by using an H ₂ SO ₄ type etching solution.
a _0.4 ) _0.5 In _0.5 P The clad layer 15 is etched halfway, and the thickness of the clad layer 15 on both sides of the stripe mesa is controlled to be 0.2 to 0.3 μm.

As a result, the first rectangular SiO ₂
Under the film, as shown in FIG. 1 (d), p-Ga _0.5 In _0.5 P
Mesa cap layer 16 is the top layer, the top layer of the mesa except the rectangular SiO ₂ film of the under second striped SiO ₂ film, as shown in FIG. 1 (c), p- (A
_{l 0.6 Ga 0.4) 0.5 In 0.5} P 0.5 cladding layer 15 is provided. In addition, the longitudinal direction of the rectangular SiO ₂ film is the resonator direction, and the rectangular SiO ₂ film having a length of 280 μm is 30
They are arranged at a pitch of 0 μm.

Then, by the second MOVPE growth, a thickness of 0.6 μm is formed on the mesa portion excluding the stripe-shaped SiO ₂ film mask.
m (flat portion) n-GaAs current blocking layer 17 (n concentration 1
× 10 ^{1 8} cm ^-3) selectively grown form. Then Si
After removing the O ₂ film mask, by the third MOVPE growth,
3 μm thick p-GaAs contact layer 18 on the entire surface
(P concentration of 5 × 10 ¹⁸ cm ⁻³ ) is grown and formed, and the p-side electrode 19 is formed on the contact layer 18 and the n-side electrode 20 is formed on the n-GaAs substrate 11. The wafer is completed.

Here, as shown in FIG. 1B, since the p-Ga _0.5 In _0.5 P cap layer 16 is not formed in the BB cross-section region, the p-GaAs contact layer 18 and the p-GaAs contact layer 18 are formed.
A junction with the (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P _0.5 cladding layer 15 is formed, and the electrical resistance increases due to band discontinuity, resulting in a current non-injection region. Further, this region is formed from both end faces of the resonator to 10 μm (X in the figure) inside the resonator, and it is possible to reduce the influence of heat generation in the vicinity of the end face due to current injection, and it is possible to perform high output operation. Also, in this example,
In the case where the width X of the current non-injection region is 10 μm, X ≧ 5
If it is μm, the effect of the present invention is not impaired.

(Embodiment 2) FIG. 2A is a perspective view showing the structure of a semiconductor laser according to another embodiment of the present invention.
2B is a sectional view taken along line DD of FIG.

The growth of the davel heterostructure by the MOVPE method is performed by the same method as in the above-mentioned first embodiment. In this embodiment, the thickness of 0.2 is formed on the active layer 14 by the first MOVPE growth.
After growing form ~0.3μm of _{p- (Al 0.6 Ga 0.4) 0.5} In 0.5 P cladding layer 15, a thickness of 40 angstroms p-Ga _0.5 In _0.5 P etching stop layer 21 (p concentration 3 × 10 ¹⁷ cm ^{- 3} ) is grown and the clad layer 15 is further formed to a thickness of 0.7 μm.
Different from

In this embodiment, since the etching stop layer 21 is formed, there is an advantage that the thickness of the cladding layer 15 on both sides of the stripe mesa portion can be formed by etching with good controllability. Here, the thickness of the etching stopper layer 21 needs to be formed as thin as 40 angstrom so as not to be absorbed by the oscillation light.

[0026]

As described above, according to the present invention,
By removing the Ga _0.5 In _0.5 P layer (p-Ga _0.5 In _0.5 P cap layer 16) of the second conductivity type in the vicinity of both end faces of the resonator, a current non-injection region is formed, and during laser oscillation, The heat generation in the vicinity of the end face can be reduced, and high-power operation becomes possible, and there is an effect that a high-output operation of 10 to 15 mW, which is about 3 times that of the rated output of 3 to 5 mW, can be realized.

[Brief description of drawings]

FIG. 1 (a) is a perspective view showing a structure of a semiconductor laser according to an embodiment of the present invention, and FIGS. 1 (b), (c) and (d) are
It is the AA line sectional view, the BB line sectional view, and the CC line sectional view which are each shown in FIG.1 (a).

FIG. 2 (a) is a semiconductor laser of another embodiment of the present invention.
It is a perspective view which shows the structure of Z, FIG.2 (b) is D- of FIG.2 (a).
It is a D line sectional view.

FIG. 3 (a) is a conventional lateral mode control type AlGa.
FIG. 3B is a perspective view showing the structure of an InP-based visible light semiconductor laser, and FIG. 3B is a sectional view taken along the line EE in FIG.

[Explanation of symbols]

1, 11 ... n-GaAs substrate 2, 12 ... n-GaAs buffer layer 3 ... n-AlGaInP clad layer 4 ... GaInP active layer 5 ... p-AlGaInP clad layer 6 ... ... p-AlGaInP cap layer 7, 17 ... n-GaAs current blocking layer 8, 18 ... p-GaAs contact layer 9, 19 ... p-side electrode 10, 20 ... n-side electrode 13 ... n- (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P clad layer 14 ………… Ga _0.5 In _0.5 P active layer 15 ………… p− (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P clad layer 16 ………… p−Ga _0.5 In _0.5 P cap layer 21 ………… p-Ga _0.5 In _0.5 P etching stop layer

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[Procedure amendment]

[Submission date] June 18, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

Claims (3)

[Claims] 1. A semiconductor laser in which a double heterojunction structure formed on a semiconductor substrate is composed of (Al _x Ga _{1 -x} ) _0.5 In _0.5 p system, at least an active layer of which is a first clad of a first conductivity type. A semiconductor layer having a refractive index higher than that of the active layer of the first conductivity type, and sandwiched between the layer and a second clad layer having a second conductivity type stripe mesa shape, and on the side of the stripe mesa and outside. The second conductivity type Ga _0.5 I is formed only on the upper surface of the second mesa of the stripe type mesa except for the vicinity of the resonator end.
A semiconductor laser comprising an n _0.5 P layer
The. 2. A second conductivity type Ga _0.5 near both end faces of the resonator.
2. The semiconductor laser according to claim 1, wherein the current non-injection region formed by removing the In _0.5 P layer has a width of at least 5 μm or more. 3. The semiconductor laser according to claim 1, wherein the second clad layer having the second conductivity type striped mesa shape has an etching stopper layer formed between the layers.