JPS63278393A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a surface light emitting laser having a low threshold current by forming a waveguide perpendicularly to an active layer, and inclining the contact at a specific angle. CONSTITUTION:A reflecting film 1-9 is formed on the inclined end face formed substantially at 45 deg. at the part corresponding to the cleaved face of a refractive index waveguide type semiconductor laser provided on a substrate 1-1, and an optical guide 1-13 is provided perpendicularly to an active layer 1-4 to a reflecting face formed on the substrate 1-1 by the film 1-9. A resonator is formed of the layer 1-4, the optical guide 1-13, and the reflecting face on the substrate 1-1. When ohmic electrodes 1-7, 1-10 are conducted, a laser oscillation output is obtained by a circular window 1-11. Thus, a laser of a low threshold value current is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser used as a light source in long-distance optical communication systems and the like.

BACKGROUND OF THE INVENTION The practical application of conventional technology optical communication in various fields is progressing steadily. At the same time, with the diversification of systems, the technology used in conventional long-distance, large-capacity backbone transmission systems has come to be applied to end-end transmission systems, including broadband transmission systems for public communications. Therefore, in addition to high performance characteristics, each related element is now required to be compact, highly reliable, high cost performance, and high productivity.

Semiconductor lasers, which are one of these elements, have been advanced in improving the performance of light sources for long-distance, high-capacity transmission, mainly using the low-loss wavelength band of fibers, and the axial mode of oscillation is stable even during high-speed modulation. A dynamic single-longitudinal mode laser is essential.

Among these, the laser for which a patent application has already been filed has advantages such as high productivity because it is an etched mirror type, and ease of coupling with a fiber because it emits surface light. A cross-sectional view of this laser is shown in FIG. The structure of this laser is, for example, on an n-InP substrate 1, an n-InGaAsP etching layer 71 layer 2, an n-InP cladding layer 3, an n-
An InGaAsP active layer 4, a p-1nP cladding layer 6, and a p-1nGaAsP cap layer 6 are sequentially grown.

Both ends of the active layer 40 are etched at an angle of 45°, and a reflective film 9 made of Si○2/Sl/Au is formed on the etched surfaces. Next, a circular window 11 is formed by etching from the substrate 1 side so that its center is directly below the point where the active layer 4 and the reflective film 9 come into contact. This etching stops at the etching stop layer 2. After removing the etching stop layer 2, a 5i3N3SIO2 multilayer film 12 is attached. This multilayer film 12 has a strong reflectance only at the emission center wavelength and enables single-longitudinal mode operation. Finally, ohmic electrodes 7 and 10 are attached to complete the laser device.

Problems to be Solved by the Invention The laser as described above has a resonator structure in which light from the active layer 4 is reflected on the reflective surface 9, further passes through the cladding layer 3, and is reflected by the multilayer film 12. ing. Therefore, when the light reflected by the multilayer film 12 spreads, it cannot return to the active layer 4 again, resulting in a large loss. For example, if the thickness of the active layer is 0.15 μm and the thickness of the cladding layer 3 is 0.6 μm, the only light that returns to the active layer will be light with a light divergence angle of 40 or less, and the thickness of the cladding layer 3 and There is a problem in that scattering on the surface of the multilayer film 12 increases the oscillation threshold current.

Means for Solving the Problems In order to solve the above problems, in the present invention, Zn is diffused between the portion where the reflective surface and the active layer contact and the multilayer film 12 to form a waveguide structure. That is, the waveguide was formed in a direction perpendicular to the active layer. When ZD is diffused into InP, the refractive index increases by about several percent.

Therefore, it is possible to effectively configure a waveguide in the InP cladding layer, and as a result, a laser with a low threshold current can be realized.

Example This will be explained below using examples.

(Example 1) FIG. 1 is a cross-sectional view of a semiconductor laser of the present invention. n-
On the InP substrate 1-1, n -InGaAs P x
, Chiguest layer 1-2. n-InP cladding layer 1-3. n-InGaAsP active layer 1-4. P-InP
A cladding layer 1-5 and a P-InGaAsP cap layer 1-6 are grown. n-InGaAsP active layer 1-
Composition No. 4 corresponds to an emission wavelength of 1.3 μm.

A S 102 film is then deposited on the growth surface, and holes approximately 2 μm in diameter are drilled in the SiO 2 by means of photolithography at intervals of approximately 200 μm. In addition, at least n-
Zn is solid-diffused to a depth that reaches the InGaAsP etchant 21 layer 1-2. This diffusion causes Zn to diffuse into a cylinder in a part of the active layer, forming a waveguide.

Next, the S to 2 film is attached again, and photoetching is performed to selectively leave Sio2 in a stripe shape of approximately 2 μm width. At this time, alignment is performed so that the diffusion portion is on the line of the stripe. Next, this striped Si○
2 as a mask, at least the n-InP cladding layer 1
The growth layer is etched to reach -3 and processed into an inverted mesa shape. This etching reduces the active layer width to approximately 1.
It becomes 6 μm. By the second growth, p-I nP
, n-1nP, to form a current blocking layer. After that, the S102 film serving as a mask was removed, and a 200 μm film was applied in a 2 μm circular shape throughout the active layer.
A laser wafer having a so-called buried structure in which Zn is diffused at intervals of m is produced. Next, reactive ion beam etching is performed on the slope 450 using Cλ gas so that the Zn diffused portion and active layer of this wafer are exposed to the outside. Next, after mask-depositing the ohmic electrodes 1-7,
A resist is applied and a reflective film 1-9 of S i O2/S i /Au is attached. Next, the film on the ohmic electrode 1-7 is removed together with the resist. Afterwards, cut the back side about 8
By polishing to a thickness of 0 μm, attaching an ohmic electrode 1-1o, opening a circular window of about 100 μm directly under the Zn diffusion layer by photolithography, and etching the crystal with HCl2, n -I n G is formed. a
A s P stops at the etching stop layer 1-2. Next, the electrode 1-10 is masked with a resist, and S13
N4/S iO2 multilayer films 1-12, each with 225
0 people and 1630A thickness, how many pairs are worn in 5 pairs? The film on the electrode is removed together with the resist.

Through the above steps, the surface emitting laser of the present invention is completed.

When the ohmic electrodes 1-7, 1-10 of such a laser were energized, laser oscillation output was obtained from the circular window 1-11. The oscillation threshold current is 20mA to 30mA. This is a dramatic improvement in characteristics compared to 4 ohmA to 60 mA without Zn diffusion.

(Example 2) In Example 1, a buried structure (BH type) was created in which the active layer was first grown by the first growth and then buried with a current blocking layer after Zn diffusion, but in this example, 1. A structure in which the current blocking layer is grown in the first step, and after grooves are formed, the active layer is formed in the second step (BCS type, Oshima et al., National, Technical.

Report volume 29, steaming 6. PP776 to 784) were first constructed, Zn with a diameter of approximately 2 μm was diffused onto the active layer at intervals of 200 μm, and then a structure similar to that of Example 1 was created, and a similarly low threshold current was obtained. Ta.

Effects of the Invention As described above, in the present invention, a surface emitting laser with an extremely low threshold current can be obtained by forming a waveguide in the vertical direction in the active layer and inclining the contact portion at an angle of 45°.

[Brief explanation of the drawing]

1-1---n-InP substrate, 1-2...n-
InGaAsP etching stop layer, 1-3...
・・n-InP cladding layer, 1-4---・n-I
nGaAsP active layer, 1-5...p-InP cladding layer, 1-6...p-InGaAsP gap layer, 1-7.10...ohmic electrode, 1-
9...5lo2/Si/Au reflective film, 1-11
-...Circular window, 1-12...5isN4/S
t○2 multilayer film. Name of agent: Patent attorney Toshio Nakao and one other person I
-7---7Z-1nP lk board/-2--n-171GoASPL Tsu'fy Coustoff Shoulder/-3--n-1nP')5-A;)i4/-4--
-71-17? GaAsPub21n/-5---P-
Ta P clad 7 duck/-6---P-171Ga71SP'<ftF1/-
7, IQ---Omi Tsuku 11 skills/-9---3r
Oz/ship/Au reflector///-- one-round type and 1-72~--3; 3Na/5rOz increase by 7%/-/3
---Z Kasuke, San 1 Figure 1/ ---7l-htP5kari 2---n-xytGaAsP etching stop 1 3-11-I p clad 1 4-11-InQ mountain AsP error-5---P-17LP Clad shoulder 6---P-1ytGtrAsP%gTsubuno17 I
Q---Ohmic Hide A blood? ---3iOz/32/AIA or A1 danger/l-m=
Circular shape and /2----3jsNJStOrz polygon 2 Fig. 6 Contents of amendment Procedures Amendment 1 Display of case 1986 Patent Application No. 114112 2 Name of invention Semiconductor laser 3 Person making correction Case and Related Patent Application Address 1006 Kadoma, Kadoma City, Osaka Name Name
(582) Matsushita Electric Industrial Co., Ltd. Representative Tani
Akio I 4 Agent 571 Address Matsushita Electric Industrial Co., Ltd. 1006 Bold Kadoma, Kadoma City, Osaka Prefecture (1) Correct "semiconductor laser" in line 7 of No. 2 of the statement to "semiconductor laser" . (2) Page 3, line 17 Norr S l s N3S
102 J e "Correct to S t 3N 4/S 102 J.

Claims (4)

[Claims] (1) It has an active layer, and has a reflective film formed on an inclined end face where a portion corresponding to a cleavage plane of an index-guided semiconductor laser provided on a substrate is processed to an angle of approximately 45°, An optical waveguide is provided in a direction perpendicular to the active layer between a film and a reflective surface provided on the substrate, and a resonator is configured by the active layer, the optical waveguide, and the reflective surface on the substrate. semiconductor laser. (2) The semiconductor laser according to claim 1, wherein the semiconductor laser is of a refractive index waveguide type in which an active layer is grown by the first growth and a current blocking layer is formed by the second growth. (3) growing a current blocking layer through the first growth;
2. The semiconductor laser according to claim 1, wherein the semiconductor laser is of a refractive index waveguide type in which an active layer is formed by second growth. (4) The semiconductor laser according to claim 1, wherein the waveguide formed perpendicularly to the active layer is formed by zinc diffusion.