JPS59220985A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain the titled device of high reliability having no contamination and no defect in spite of formation of the resonator end surface by etching by a method wherein an active layer or the substantial excitation region is provided inside the end surface at a position alienated from the end surface, in the laser device having the hetero junction structure consisting of the active layer and a clad layer. CONSTITUTION:On an N type GaAs substrate 1, an N type GaAlAs main clad layer 2, an N type GaAlAs auxiliary clad layer 3, a P type GaAs active layer 4, a P type GaAlAs auxiliary clad layer 5, a P type GaAlAs main clad layer 6, a P type GaAs ohmic contact layer 7 are epitaxially grown by lamination. Next, a GaAlAs mask layer 21 is provided on the layer 7 and covered with a stripe resist 22, and then this laminated body is changed into a mesa form reaching the substrtate by etching. Thereafter, the resist 22 is removed, this laminated body is buried in a GaAlAs layer 8 provided on the substrate with the layer 21 as a mask, and the resonator end surface is positioned in the layer 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor laser device having a heterojunction structure, and more particularly to an improvement in a semiconductor laser device in which a resonator end face is formed by etching.

[Technical background of the invention and its problems]

Currently, a cleavage plane of a crystal is generally used as the cavity end face of a semiconductor laser. However, cleaving the crystal is a manual process with extremely low productivity, and this is a major factor preventing the cost reduction of semiconductor lasers. Further, the development of so-called 0EIC, which integrates a semiconductor laser with other light-emitting/light-receiving elements, electric circuits, etc., is progressing, but in this case, it may not be possible to use the method of forming the resonator end face by cleaving.

Therefore, recently, so-called etching facet lasers, in which the resonator end faces are formed by various etching methods such as wet etching and plasma etching, have been attracting attention. When a crystal is etched, usually side etching occurs in the lateral direction depending on the plane orientation of the crystal at the same time as etching in the depth direction, and the etched side surface does not become vertical. However, under certain etching conditions, the etched side surface becomes vertical without side etching. can get. Etched facet lasers often use etched side surfaces perpendicular to Q as a resonator, and by using this method, the resonator end face can be formed monolithically. Since multiple resonator edges IfJ can be formed in a single etching process using a mask, resist, etc., productivity is significantly improved compared to the laser etching method that uses cleavage planes. It also becomes possible to form laser end faces. Furthermore, there is no need to perform a substrate polishing step or the like that accompanies cleavage, and from this point of view as well, the manufacturing process can be simplified.

However, when the resonator facets are formed by etching, a problem arises in that the reliability of the semiconductor laser is lowered due to direct etching of the active region. That is, in the vicinity of the activated resonator end face, laser light is reabsorbed and heat is generated, creating a state in which chemical reactions and growth of crystal dislocations are likely to be promoted. Therefore, when the end portion is formed by wet etching, for example, the end surface is likely to react with residual etching solution and moisture, causing deterioration of the end surface. Furthermore, when plasma etching is used, ions and active species directly collide with the active region. For this reason, the active region is damaged by radiation and crystal defects and dislocations are introduced into the active region, which in turn causes end face deterioration and oscillation stoppage, leading to a decrease in the reliability of the semiconductor laser.

[Purpose of the invention]

An object of the present invention is to provide a semiconductor radar device that can prevent crystal defects and dislocations from occurring in the active region even though the resonator end face is formed by etching, and can improve reliability and reduce costs. It's about doing.

[Summary of the invention]

The gist of the invention is to arrange the end of the active layer or its substantial excitation region inside the resonator end face.

Some kind of contamination or defect occurs on the crystal surface etched by various methods. The decrease in reliability that occurs when forming the resonator end face of a semiconductor laser by etching is
This is caused by the introduction of these contaminants and defects into the active region (the active layer or its substantial excitation region) near the end face, which is particularly highly reactive and prone to growth of defects. Therefore, if the resonator end face can be formed without directly etching the active region, it is considered that reliability will not deteriorate.

The present invention focuses on these points, and in a semiconductor laser device in which a petrojunction tank structure consisting of an active layer and a cladding layer is formed on a semiconductor substrate, a laser resonator end face is formed by etching, and the active layer is etched. The layer or its substantial excitation region is formed at a position spaced from the resonator end face and on the inner side of the end.

〔Effect of the invention〕

According to the present invention, since the active layer or the active region, which is a substantial excitation region thereof, is separated from the resonator end facet, the active region is not affected by contamination or defects introduced by etching.

Moreover, since the vicinity of the end face is in an extremely active state, reactivity is poor and dislocation growth is difficult to occur. Therefore, even though the resonator end face is formed by etching, a decrease in reliability can be prevented. This is extremely effective for mass production and cost reduction of semiconductor lasers.

[Embodiments of the invention]

1 and 2 are for explaining one embodiment of the present invention, and FIG. 1 is a perspective view showing a schematic structure of a semiconductor laser device having an etching facet monolithically formed on a semiconductor substrate. , Figure 2 shows the above board.
FIG. 2 is a perspective view showing a schematic structure of one semiconductor laser device. 1 in the figure is an n-GaAII substrate (semiconductor substrate)
On this substrate 1 are n-GaO, 65AtO,
35As layer (main cladding layer) 2,n''-Ga0.75
At0.25 As layer (auxiliary cladding layer) 3, p −
GaAs layer (active layer) 4, l'l -Ga175 At
O,2S As layer (auxiliary cladding layer) 5) pGf106
5Δto, xs As layer (main cladding layer) 6 and p −
A mesa strip section is provided by stacking GaAs)'74 (ohmic contact M)7 on the above 110. The side and end surfaces of the mesa stripe part are GaO,
65Ato, 55As buried by a buried layer 8. The resonator end face 11 is monolithically formed by etching the region of the buried layer 8, as shown in FIG. In the figure, 12 is an insulating film for current confinement, 13.
14 indicates an electrode.

FIGS. 3(a) to 3(d) are perspective views showing the manufacturing process of the GaAtAs embedded laser shown in FIGS. 1 and 2 above. First, as shown in FIG. 3(a), a main cladding layer 2, an auxiliary cladding layer 3, an active layer 4, an auxiliary cladding layer 5, a main cladding layer 6, and an ohmic contact layer 7 are formed on a substrate 1.
and Ga o, 411 o, 6 As layer (selective mask during buried growth) 21'f: epitaxially grown on the above Jl. Next, as shown in FIG. 3(b), a striped photoresist mask 2 is formed on the selection mask 21.
2 and using a reactive ion etching method using a mixed gas mainly composed of CCl< and C12 as a reactive gas,
Using the photoresist mask 22 as a mask, the layers 2 to 7 and 21 are mesa-etched to a depth that reaches the substrate 1. Next, using the GaAlAs layer 2 as a selection mask, the mesa region is buried with a buried layer 8 using the LPE method as shown in FIG. 3(c).

Subsequently, the selective mask 21f is removed, and the insulating film 12f is formed only on the buried layer 8. Thereafter, Cr/Au is deposited as a p-side electrode 13 on the insulating film 12 and the ohmic contact layer 7, and AuGe/Au is deposited as an n-side electrode 14 on the lower surface of the GaAs substrate 1.

Next, as shown in FIG. 3(d), a photorenost mask 23 is formed on the p-side electrode 13 so as to cover the mesa region and a part of the buried layer 8, and the end thereof is perpendicular to the mesa stripe. do. Thereafter, the P-side electrode 13 is etched using the photoresist mask 23 as a mask using a reactive ion etching method using a reactive gas mainly composed of ct2, and then the buried layer 8 is etched using a reactive gas mainly composed of ct2 and cct4. is etched down to the substrate 1. At this time, by selecting etching conditions in which the etched side surfaces are vertical, a resonator end face is formed in the m-embedding layer 8, and thus a plurality of semiconductor lasers can be formed on one substrate as shown in Fig. 81!1. It becomes possible to form it monolithically.

In this way, according to this embodiment, since the resonator is formed in the non-active region, not only its life characteristics are improved, but also damage at the end face of the resonator is less likely to occur, compared to the conventional one. High output operation is possible. Furthermore, since the end of the active layer 4 is buried with the buried layer 8 having a wide forbidden band width, the resonator end ml has poor reactivity and almost no growth of dislocation occurs. Therefore, reliability can be improved and costs can be reduced, with great results.

Note that the present invention is not limited to the embodiments described above. In the embodiment described above, the entire heterojunction structure on the resonator side is buried with the buried layer 8, but it is not necessarily necessary that the entire Peter structure is buried as long as the active layer 4 is buried. For example, as shown in FIG. 4, even if part of the auxiliary cladding layer 2, part of the main cladding layer 3, or part of the optical waveguide layer is not used for the resonator end face, the effects of the present invention are not impaired in any way. Furthermore, the end of the active layer 4 does not necessarily have to be buried in the buried layer 8, and as shown in FIG. That's good. In the example shown in FIG. 5, a striped electrode 13 is formed on the inner side of the end face of the resonator, and the excitation region of the active layer 4 is formed on the inner side of the end face of the active layer 4 due to the electrode 13. stipulated. In this case as well, the resonator end face becomes an inactive region, so that the effects of the present invention can be sufficiently obtained.

Furthermore, the semiconductor material is not limited to GaAtAs-GaAs, but may also be InGaAaP-InP or other various semiconductors. Furthermore, the structure of the semiconductor laser does not have to be a buried structure, and various structures can be used. Further, the etching method for forming the resonator end face is not limited to reactive ion etching, and may be any etching method in which the etched side surface is vertical. Other modifications can be made to the MI without departing from the spirit of the present invention.

[Brief explanation of the drawing]

1 to 3(a) to 3(d) are for explaining one embodiment of the present invention, and FIG. 1 shows a semiconductor laser device having an etching facet monolithically formed on a semiconductor substrate. FIG. 2 is a perspective view showing the schematic structure of one embedded semiconductor laser device protruding from the substrate, and FIGS. 3(a) to (d) show the semiconductor laser device FIGS. 4 and 5 are perspective views for explaining modified examples, respectively. 1...n-GaAs substrate (semiconductor substrate), 2...
n-GaO, 65At0j 5 As layer (main cladding layer), +9- n-GaO, 75AtO, 25As layer (auxiliary cladding layer)) 4°" p-GaAs layer (active layer), 5- p-GaO, 75A4 .25 As layer ((
auxiliary cladding layer), 6'''r'-GaQ, 65
ALo, 55A 8 layers (main cladding layer), 7 = -p -
GaAs layer (ohmic contact layer), 8-=Ga
065 kl (3,55 As layer (buried layer), 11
...Resonator end face, 12...To insulation 11, 13, 1
4-...electrode, 21-Gao, 4, kt□, 6 A
s layer (selective mask), 22.23...photoresist mask. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 3

Claims (3)

[Claims] (1) In a semiconductor radar device in which a heterojunction structure consisting of an active layer and a cladding layer is formed on a semiconductor substrate, a laser resonator end face is formed by etching,
A semiconductor radar device characterized in that the active layer or its substantial excitation region is formed at a position apart from the resonator end face and on the inner side of the end face. (2) The end portion of the active layer is buried with a buried layer having a larger forbidden band width than the active layer, and the end face of the resonator is formed by etching the buried layer. A semiconductor laser device according to claim 1. (3) The substantial excitation region of the active layer is defined by the shape of the striped electrode, and the resonator end face and the end of the active layer are formed in the same plane, and the striped electrode is defined by the shape of the striped electrode. 2. The semiconductor radar device according to claim 1, wherein the electrode is formed on the inner side of the end face of the resonator at a position apart from the end face.