JPH01132189A - Semiconductor laser element and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser element which is operated stably up to a high output in transverse fundamental mode by a method wherein a current constriction layer is provided at both ends of a stripe-like mesa-shaped clad layer and at least a part near one reflection face is made transparent or the like. CONSTITUTION:At least a double heterostructure composed of a first semiconductor clad layer 2, a second semiconductor active layer 3 and a third semiconductor clad layer 4 which have been laminated one after another on a semiconductor substrate 1 is contained; the third semiconductor clad layer 4 has a stripe-like mesa shape along an axial direction of a resonator in which a beam is guided; at least its part near a reflection face on one side is made transparent; a fourth semiconductor current- constriction layer 11 is formed in a part other than said stripe-like mesa shape. For example, a first semiconductor clad layer 2, a second semiconductor active layer 3 of a quantum well type, a third semiconductor clad layer 4 are formed on a semiconductor substrate 1; after that, an impurity is diffused in a neighboring region including a part used as an end face of a semiconductor laser element; the active layer 3 of the quantum well type is made a mixed crystal, and is made transparent with reference to a laser oscillation wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device that operates stably with high optical output.

[Conventional technology]

Semiconductor laser? When operating at high output, one of the factors that reduces reliability is the problem of end face deterioration. This is because (1) light absorption normally occurs in surface states formed at the end face of a semiconductor laser, which causes a rise in temperature at the end face, which causes a vicious cycle in which the band gap narrows and further absorption increases. This problem is caused by AtzO3 on the end face.
However, it can be improved to some extent by applying coating treatments such as

Furthermore, in order to obtain high reliability with high output operation, it is necessary to make the end face transparent. One solution to this is.

[Applied Physics Letters, Vol. 34, No. 10, Paragraphs 637-639, (Appt 1edphy
sics, I, etter, Vol, 34.
&10 pp637-639 (1979))j
It is stated in In this semiconductor laser, Zn is diffused into the active layer except for the end facets, and the non-diffused end facets are made transparent by making the oscillation wavelength longer due to the impurity level, thereby achieving high output.

[Problem that the invention seeks to solve]

The above conventional technology does not consider stabilizing the fundamental mode of the single oscillation mode, and when applied to devices using semiconductor lasers such as single-source disks and laser beam printers,
There were problems such as unstable operation.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art as described above and to provide a semiconductor laser device that stably operates in a transverse fundamental mode up to a high output.

[Failure to solve the problem]

In order to achieve the above object, in the present invention, a first semiconductor cladding layer of a 1st conductivity type is formed on a semiconductor substrate of a 1st conductivity type,
After forming at least a quantum well type second semiconductor active layer consisting of a well layer and a barrier layer, and a third conductivity type third semiconductor, a dielectric film is formed on one surface, and using this film as a mask, at least one reflective surface is formed. The quantum well type active layer near the reflective surface is made into a mixed crystal by diffusing impurities or implanting ions in the vicinity.

Thereafter, a striped etching mask is formed on the surface along the resonator axis, and the dielectric mask and the third semiconductor cladding layer are etched. next.

Use the dielectric mask to cover areas other than the mask part.

The structure is selectively provided with at least a first conduction type current confinement layer or a high resistance current confinement layer.

[Effect]

In the structure of the present invention, near the end face of the semiconductor laser, the quantum well type active layer is made into a mixed crystal by impurity diffusion or ion implantation, and becomes a semi-solid layer with an average composition. At this time, if the semiconductor layer is designed so that the band gap of the average composition is large in energy corresponding to the excavation wavelength of the laser, the vicinity of the end face can be made transparent. This results in
It is well known that end face deterioration during high power operation can be significantly improved. Furthermore, by etching the dielectric mask and the third semiconductor cladding layer by using an etching mask along the cavity axis direction, it becomes possible to form a ridge-type optical waveguide, resulting in a stable transverse fundamental mode. Oscillation is obtained. Further, by using the dielectric mask etched into stripes as a mask for selective growth, the current confinement layer is formed in a self-aligned manner. This self-alignment method simultaneously improves manufacturing accuracy and simplifies the process. In addition, in the semiconductor laser with this structure, a current confinement layer is formed near the end facet, so it is possible to prevent invalid current from flowing near the end facet, resulting in lower threshold current values and higher reliability. More will occur.

〔Example〕

An embodiment of the present invention will be described below.

Example 1 A high-power semiconductor laser device according to Example 1 of the present invention is shown in FIG.
a) to ゛This will be explained using FIG. 1(C) and FIG. 7g2.

First, as shown in FIG. 1(a), an n-type GaAs substrate 1
((100) plane, 3i doped, n~lX10"cm-
”) on top, Qrgano Metallic vapo
r phase Epitaxy (OMVPE) method 1
1CL Tsu1n-Gao, ss Ato, 45AS
Cladding layer 2 (Se)''-p.

n ~ l x 10"cm-"#thickness approx. 2 pm
), Ga As well layer 80 people e Gao,
y Ato, s A S Barrier layer 120 people alternately 5
Multiple quantum well type active layer 3 e pG aO,
ss At6,45 A S cladding layer 4 (Zn doped, p~6 x 101?cm-", thickness about 1.2μ
m).

p-QaAS interface layer 5 (Zn doped, p~i
x10 ''cm-'', thickness approximately 0.1 μm) 1, and a SiNx diffusion mask 6t- was formed thereon.

Next, an opening was made in a portion 7 near the end face of the semiconductor laser, and 5kin was thermally diffused to make the end face portion 8 of the multi-quantum well type active layer 3 into a mixed crystal. Next, as shown in FIG. 1(b), a striped photoresist mask 9 is provided along the laser cavity axis direction.

The 8rNx diffusion mask 6 is etched into stripes, and the pGaAs interface layer 5 is etched.
．． and etching pGao, HAto, 4s ASI 4.

An optical waveguide ridge 10 having a width of about 5 μm was formed. next,
As shown in FIG. 1(C), the photoresist mask 9
After removing the n-GaAs current confinement layer 11 (Se-doped,
n-w4XlO"cm-", thickness of about 0.7 μm in the outer region of the ridge) was selectively formed on the SiN and the portions other than the mask 6. Then, as shown in FIG. 2, after removing the 5iNx mask 6.

pGao, ss kla, as As buried layer 12 (Znn doped p~I X 10" crn-
', thickness approximately 1 μm), p-GaAS cap layer 1
3(Zn-doped*p~IX10"(yB-",
1 μm thick), and the p-side electrode 14. n-side electrode 15
After forming.

Cleavage and scribing were performed to create a laser chip. In this example, the quantum well type active layer 8 near the end facet of the semiconductor laser is made into a mixed crystal by Zn diffusion, so that the average composition of Ga 644 A to, 16 A S
It can be done. The semiconductor laser device of this example is 1
The oscillation wavelength is about 840 nm, and the end facet has a smaller energy than the oscillation wavelength of the laser. This made it possible to significantly reduce interband absorption at the end face. Moreover, it was provided along the resonator axis. By using the ridge-shaped waveguide structure 10, a laser device that stably oscillates in the transverse fundamental mode up to high output was obtained. In addition, the Si used for Zn diffusion
N.

The mask 6 is used to form the ridge 10 and to form the flow constriction layer 1.
By using it for the selective formation of 1, a self-aligned device manufacturing process becomes possible, and the 1 manufacturing precision is improved and the device manufacturing process is significantly simplified. Further, in the semiconductor laser of this embodiment, a current confinement layer is also formed in the vicinity of the end facet.

The reactive direct current flowing here was also reduced, which helped lower the single-oscillation threshold and improve reliability.

The semiconductor laser device of this example has a wavelength of 840 nm, l
, oscillation occurred at a threshold current value of approximately 30 mA, and stable transverse fundamental mode oscillation was obtained up to 100 mW or more.

Furthermore, since the optical waveguide is formed by a ridge up to the end face, astigmatism can be reduced to 5 μm or less.

In Example 1 of the present invention, as the material of the diffusion mask,
It has been found that a similar structure can be produced also when phosphorus glass (PSG) or 5jOz is used. The properties obtained were similar to those in Example 1. Also, as a means of mixed crystallization of a quantum well type active layer.

Instead of Zn diffusion, a combination of ion implantation and annealing was also possible.

Note that a layered film of a dielectric film and a photoresist was used as a mask for ion implantation.

Example 2 In Example 1 of the present invention, when forming the optical waveguide ridge shown in WJ1 diagram (b) by etching, after the etching was completed halfway, further etching was performed on the central portion in the axial direction of the resonator.
Mask that prevents etching (photoresist, etc.)
, and etching was performed again. This creates a deep ridge near the end face.

A shallow ridge was formed in the center, and the ridges had different depths in the axial direction of the resonator. The subsequent process was the same as in Example 1. In this example, the semiconductor laser stably oscillates in the transverse fundamental mode up to 100 mW, and operates with low noise with a relative noise intensity of 10'' Hz or less up to about 10 mW. A high-output, low-noise semiconductor laser was obtained.

Note that for shorter wavelengths, the well layer ftGaAtAS
However, in this case as well, if the average composition created by mixed crystal formation with the barrier layer is designed to a value that is transparent to the laser oscillation wavelength, the same end face deterioration improvement effect can be achieved. is obtained.

Furthermore, wet etching or dry etching can also be used as a method for forming the resonator reflecting surface.

〔Effect of the invention〕

According to the present invention, it is possible to create an optical waveguide ridge that stabilizes the transverse mode, so that a stable transverse fundamental mode can be found. Further, since the end face is made transparent by mixed crystal formation of the quantum well type active layer, the problem of end face deterioration can be significantly improved. Also.

The structure prevents current from flowing near the end face, reducing reactive current and improving reliability. Furthermore, end face transparentization 1
Since the formation of the original waveguide ridge and the selective formation of the current confinement layer can be performed in a self-aligned manner, it becomes possible to significantly improve the device manufacturing efficiency and simplify the device manufacturing process. Note that in the embodiments of the present invention, a QaAtAs-based semiconductor laser device has been described, but other material systems 1, such as I
It can also be applied to an nGaAZP thread visible laser, and its technical effects are extremely large.

FIG. 2 is an exploded view of a high-power semiconductor laser according to Example 1 of the present invention.

3...Multi-quantum well type active layer, 6...SiN! mask.

8... Mixed crystal active layer, 9... Etching mask for ridge formation, 10... Ridge for optical waveguide, 11...
n - Heron 1 Figure ￥: J 2 Day 4P-θ use 14 Pfθ・1 stillness 32ri & JtLt-immersion 1

Claims (1)

[Claims] 1. It has at least a double heterostructure of a first semiconductor cladding layer, a second semiconductor active layer, and a third semiconductor cladding layer that are sequentially laminated on a semiconductor substrate, and the third semiconductor cladding layer has an optical has a striped mesa shape along the resonator axis direction in which the wave is guided, the vicinity of at least one reflecting surface is transparent, and a fourth semiconductor current confinement layer is provided in a portion other than the striped mesa shape. What is claimed is: 1. A semiconductor laser device comprising: 2. The semiconductor laser device according to claim 1, wherein the fourth semiconductor current confinement layer is also formed near the reflective surface of the mesa-shaped third semiconductor cladding layer. 3. A quantum well type second semiconductor active layer consisting of a first conductivity type first semiconductor cladding layer, a well layer, and a barrier layer, and a second conductivity type third semiconductor cladding layer on a first conductivity type semiconductor substrate. furthermore, forming a dielectric film thereon, and using the dielectric film as a mask to perform impurity diffusion or impurity ion implantation into a nearby region including a portion that will become at least one end face of the semiconductor laser element, The quantum well type second semiconductor active layer is made into a mixed crystal to make it transparent to the laser oscillation wavelength, and further, a striped etching mask is formed on the crystal surface including the dielectric film to form the dielectric film into a stripe shape. After etching, the third semiconductor cladding layer is etched to form a striped optical waveguide ridge, and then, using the dielectric film as a mask, a fourth semiconductor current confinement of conductivity type I is formed in a portion other than the mask. layer,
Alternatively, a method for manufacturing a semiconductor laser device, characterized in that at least a fourth semiconductor current confinement layer having high resistance is formed.