JPS59103393A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of a distribution feedback type laser in the groove wave-guide type by a method wherein V-shaped grooves are formed on a semiconductor crystal layer which has been made a grown formation on a semiconductor substrate carved with diffraction gratings on the surface thereof. CONSTITUTION:A mask film 13 is formed in a stripe-form in the direction to intersect at a right angle with the groove direction of diffraction gratings 11 on an N type InP substrate 12 carved with the diffraction gratings 11 on the surface thereof. Then, a P type InGaAsP layer 14 is made a crystal growth on the substrate 12. At this time, the layer 14 is formed on both sides of the film 13. The film 13 is removed and a groove part 15 provided with the gratings 11 is formed on the bottom part thereof. An N type InGaAsP layer (clad layer) 16 and an undomed InGaAsP layer (active layer) 17 are successively grown, and, a P type InP layer (clad layer) 18 and a P<+> type InGaAsP layer (ohmic contact layer) 19 are successively made a grown formation. The distribution feedback type laser manufactured through these procedures can be significantly lessened the threshold value of oscillation current, that is, the control for low threshold value and transverse mode can be completely realized and the operation of distribution feedback can be effectively done.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a monodistribution feedback semiconductor radar.

[Technical background of the invention and its problems]

Recently, various semiconductor lasers have been developed that use a double heterojunction structure (hereinafter abbreviated as DH tank structure) made of IV group semiconductors and are capable of continuous oscillation at room temperature. I)H
A practical semiconductor laser having a structure requires a striped active region and a waveguide (resonator) in the structure. One way to realize such a structure is to
A method is adopted in which a groove having a V-shaped cross section is formed in a semiconductor substrate, and then an active layer is completely isolated in the groove by crystal growth.

FIG. 1 is a sectional view showing an example of a semiconductor laser formed by the above method. V on n-type C100) InP substrate 1
After forming the groove, an n-type InP layer 3. is formed as a cladding layer thereon. Undoped I n Ga as active layer
A s P layer 4 (band gap 1.3 μm band), a P-type InP layer 5 as a cladding layer, and an ohmic contact layer.

All P+ type InGaAsP layers 6 are grown in the above order. The active layer 4 is formed separately in a V-groove portion and has a waveguide structure. The semiconductor laser with this V-groove structure is
It is relatively easy to manufacture and reliable (fflE is also high, so it has been attracting particular attention recently.

However, the method using the groove structure described above has the following problems. In other words, the groove structure is effective in a laser that utilizes feedback from a Fan) Perot (F, P) resonator with both surfaces as resonators; It is extremely difficult to apply this method to a so-called distributed feedback type radar (hereinafter abbreviated as FB laser 1) which causes oscillation. I) In the case of an FB laser, it is necessary to provide irregularities (diffraction grating) with a constant period on a semiconductor substrate, and to provide a waveguide structure with a different refractive index in close proximity to this periodic structure. For this reason, in a structure in which a V groove is provided in a semiconductor substrate, the diffraction grating in the waveguide structure is removed due to the etching process for forming V7H<. Furthermore, with the current technology, there is a problem in that (1) the above-mentioned V-groove structure in which a diffraction grating is carved on the bottom or side surface of the groove cannot be applied.

[Purpose of the invention]

The object of the present invention is to
It is an object of the present invention to provide a method for manufacturing a semi-four-body laser, which can apply a groove-ring waveguide structure to an FB laser and can contribute to simplification of manufacturing and improvement of reliability.

[Summary of the invention]

The gist of the present invention is not the semiconductor substrate itself on which a diffraction grating is carved, but a V-groove (
The aim is to form a V-shape (not limited to a complete V-shape).

That is, when manufacturing a DFB radar, the present invention forms a striped mask film that inhibits crystal growth on a semiconductor substrate provided with a diffraction grating of a predetermined period, and then forms a mask film of a conductivity type opposite to that of the substrate on the semiconductor substrate. Alternatively, a method may be used in which a semi-insulating semi-central crystal layer is formed, the mask film is then removed to form a groove, and a DH structure consisting of an active layer and a cladding layer is then grown in the groove. be.

〔Effect of the invention〕

According to the present invention, since the recesses (grooves) are entirely formed by crystal growth after providing the diffraction grating on the semiconductor substrate, there is no inconvenience such as the diffraction grating being removed to form the grooves.
A waveguide structure can be constructed in the groove. Therefore, it becomes possible to easily fabricate a groove waveguide type DFB radar, and it is possible to improve the characteristics of a semiconductor laser by stable longitudinal mode oscillation and anechoic decoupling.

[Embodiments of the invention]

FIGS. 2(a) to (f) are 1) related to one embodiment of the present invention.
It is a perspective view and a sectional view showing the FI3 laser manufacturing process.

First, as shown in Figure 2(a), the surface is coated with a period of 2o00[X
, 1. depth 1000(X)0) n carved with diffraction grating 11
CVD on type (100) InP substrate (half-quad board) 12
-8i0. A film (mask film) 13 was formed in a stripe shape with a width of about 2 [μm] in a direction perpendicular to the groove direction of the diffraction grating 11. Note that this mask film forming step is performed using the above-mentioned CVD-8i.
0. After the film 13 has been deposited on the entire surface of the substrate 12, unnecessary portions thereof may be selectively etched using conventional wet etching or reactive ion etching techniques. Further, FIG. 2(b) shows a cross section taken along the arrow AA in FIG. 2(a), and shows that (: V D -8i0° film 13 is formed on a desired waveguide formation region.

Next, as shown in FIG.
(band gap 1.0 μm band) was grown to a thickness of about 1 μm. At this time, the CVD-8102 film 1
Since crystal growth is inhibited in the part where In3 exists, In
The GaAsP layer 14 is made of CVD-8i0. They will be formed on both sides of the membrane 13.

Next, the CVD-8in film 13 was removed using an ammonium fluoride solution or the like, and a groove 15 in which the diffraction grating 11 was provided was formed at the bottom thereof. Next, as shown in Figure 2(d), n-type InGaAs with a band gap of 1.15 [μm] was
P layer (cladding layer) 16 and Pandocats 761.3
C μm)
Active layer) 17 was sequentially grown and formed. At this time, the cladding layer 16 and the active layer 17 are separated into the groove 15.
i41F was formed, and this (two-year) striped husks”
) A wave path structure will be formed.

Then, as shown in Fig. 2(e) 17-(P Ja In
P4-type I n Ga As of P layer (cladding l(A)) I8 and non-wire gap 1.15 Cμm]
A P layer (ohmic contact 1i"i) 19 was sequentially grown and formed. "Oh, Fig. 2 (f) is the arrow in Fig. 2 (e)?
.

One diffraction grating 11 is present below the active layer 17. From this point onwards, the usual
17 layers 17 and 7t
l) j"+1'71F (ii). Second, the stripe shape of the active layer 17 enables single-transverse mode oscillation, and the light seeping out laterally is also influenced by the diffraction grating 11 and becomes D. The F B %”% structure can be more effectively exhibited.

In other words, low threshold value, transverse mode: 171J control is completely performed, and feedback by the diffraction grating 11, that is, DFB operation is effectively performed. Therefore, it is possible to improve the characteristics of stable single-longitudinal mode oscillation without any opening. Also,
This method does not require any special equipment and can be easily implemented using only the technology that is currently in practical use.

Note that the present invention is not limited to the embodiments described above. For example, the stripe width of the mask film is 2 [μm]
It is not limited to CVD-8i0. Any material other than the film may be used as long as it inhibits crystal growth. In addition, the semiconductor monthly fee is InP/InG
Not limited to aAsP system, but also GaAs/GaA, d
On As-based and other l-V group systems? It is possible to use a 1゛ body. Furthermore, the above-mentioned half-melon (the body crystal layer is always a crystal layer; (11) is a perspective view, (b) to (f)
is a sectional view.

11... Diffraction grating, 12... N-type InP substrate (semiconductor substrate), 13... CVD-8in, film [mask film]
, 14 ・P type L n Ga A SP layer (semiconductor crystal layer), I 5-... Groove, 16-11 type I n G
a As P layer (cladding layer), 17... undoped 1nGaAsP layer (active layer), :t g-P type In
P layer (crania)'fVJ) 19 ・” P to I
nGaAs Fil (ohmic core tact layer).

Applicant Makoto Ishiita, Director of the Agency of Industrial Science and Technology Figure 1 Figure 2 Figure 2 B

Claims (1)

[Claims] A method for manufacturing a distributed feedback semiconductor laser includes the steps of forming a striped mask film for inhibiting crystal growth on a semiconductor substrate provided with a diffraction grating of a predetermined period;
Next, a step of growing a semiconductor crystal layer of a conductivity type opposite to that of the substrate or semi-insulating on the semiconductor substrate, a step of removing the mask film to form a groove, and forming an active layer and a cladding layer in the groove. A method for manufacturing a semiconductor laser, comprising the step of growing a double heterojunction structure consisting of: