JPS5864084A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To allow a semiconductor laser to be hardly affected by mechanical damage and to have long lifetime by providing a semiconductor substrate having two parallel grooves, an active layer formed on the substrate and a current blocking layer having a defect at the projection between the two grooves in the improvement of the buried type laser and having a main light emitting region of part of the active layer formed on the projection. CONSTITUTION:Two parallel grooves 12 are formed on an n-IP substrate 11 having a main surface in (100) plane along crystal azimuth (011). A buffer layer 15, active layers 16a, 16b, 16c, the first clad layer 17, a current blocking layer 18, the second clad layer 19 and a cap layer 20 are sequentially grown by a liquid growing method. The layer 18 is grown with defect on the projection 12 by selecting the suitable growing condition. The layer 16 made of InGaAsP is formed with stepwise disconnection. Since the current blocking layer is made defective on the layer 16a, the current is concentrically injected to the layer 16a. In addition, the layer 16a is formed substantially in the same height as the other most part of the layer 16c, the projection is hardly subjected to the mechanical damage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in semiconductor lasers, particularly buried structure semiconductor lasers.

Figure 1 shows a conventional current confinement mesa substrate buried structure laser (Curre), which is a type of buried structure semiconductor laser.
nt Confcnement jdesa-5ubs
tvateBuried Heterc-8truct
uve Lamer Diode (abbreviated as CCM-LD)
A cross section of is shown. The CCM-LD has an active layer (InG, aAiP) formed on a protrusion 2 formed on an Inpn plate substrate l, as shown in Material 0QE80-117 of the Photon Quantum Electronics Study Group of the Japan Society of Electronic Communications.

λg ~ 1.3 μm) 4a, active layers (I
n Ga As P *λg~1.3,1m)4
The active layer 4a has a so-called buried structure in which the active layer 4a is surrounded by a buffer layer 7 (n-InP) 3 and a first cladding layer (p-InP) 5 having a small refractive index. ing. In addition, a current blocking layer (H-(n
Since P) 6 is missing on the central origin 112 and is formed only on both sides, current can be efficiently concentrated in the active layer 4a. This CCM-LD crystal is formed by a sliding method, which is a type of liquid phase growth method. After forming the active layers 4a and 4b in this liquid phase growth, the first cladding layer 5
, when forming the current blocking layer 6, since the active layer 4a is on the protrusion 2, it protrudes from other regions,
It has the disadvantage that it easily comes into contact with the liquid-phase growth boat and is therefore susceptible to mechanical damage, resulting in crystal breakage and dislocation generation.

Made from crystals that have undergone such mechanical damage, it costs 900M.
-LDs had the drawbacks of high deterioration rate when energized and short lifespan.

An object of the present invention is to provide a semiconductor laser whose active layer is less susceptible to the above-described mechanical damage and has a long life.

According to the present invention, there is provided a semiconductor substrate having two grooves each having a thousand rows, an active layer formed on the semiconductor substrate, and the above two grooves.
There is obtained a semiconductor laser characterized in that the protrusion between the two grooves is provided with a current blocking layer having a defect, and a region of the active layer formed on the protrusion is used as a main light emitting region.

The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a cross-sectional view of one embodiment of the present invention.

In the figure, 11 is an n-In in which $13 parallel to each other is formed.
P substrate, 15 is a buffer single layer (n-InP, Jl~0
．． 5 μm), 16L 16b, 16C are active layers (InG
mAsP, λg ~ 1.3 μm, rhinoceros size ~ 0.2 μm), 1
7 is the first crat layer (p-InP, thickness ~0.7 μm)
1 B is a current blocking layer (n-Inp, thickness ~0.7 μm
), 19 is the second crat layer (p-InP, thickness 2-5μ
m), 20 is a cap layer (pI n Ga As
P, λg ~ 1.3 μm + thickness ~ 1. am), 21
is a Pt electrode, and 22 is an n electrode.

The main active region of the buried structure laser of this example is:
Since the active layer is formed with a step break at the step of the active layer 16a formed on the protrusion 12, the groove 13
The active layer 16b formed at the bottom of the active layer 16b is discontinuous with the active layer 16a and the active layer 16C. Further, the current blocking layer concentrates the rounded current lines missing on the active layer 16a.
6a. The ring on the upper side of the protrusion 12 is approximately 2 μm1
The groove 13 has a width of 5 to 10 μm and a depth of about 3 μm, and the flat portion 1
4 has a width of 100 to 150 μm.

Now, in FIG. 2, active layer 1 which is the main active region
6.11 shows that even the active layer 16C on the flat portion 14 does not protrude. That is, although the active layer 16a is formed on the protruding portion 12, it is located at the same height as the active layer 16C on the flat portion 14 and does not protrude.

From this, when the crystal of the buried structure semiconductor laser of this example is formed by the m- slide method of liquid phase growth, the active layer 16a is at the same height as most of the other active layers 16C. In some cases, the mechanical damage caused by the protrusion contacting the boat, which was the case in the past, has almost completely disappeared.

Briefly describe the manufacturing method of the buried structure semiconductor laser of this example II. n-InP whose main surface is the (100) plane
Two mutually parallel grooves 12 are formed along the <011> crystal orientation on the substrate 11 by photoetching. Next, a buffer layer 15 and an active layer 16a are formed by a sliding method, which is a type of liquid phase growth method.

16b, i6c first cladding layer 17, current blocking layer 18, second cladding layer 19, and cap layer 20 are successively grown. In this case, by selecting excessive growth conditions, the buffer layer 15 and #, l cladding layer 17 grow on the protrusion 12, but the t-flow blocking layer 18i! It grows on the protrusion 12 in a defective manner. Further, the active layer made of InGaAsP does not grow on the side surface of the protrusion, but is formed with steps. After polishing the thus obtained iza crystal to a thickness of approximately 100 μm, a Pi electrode 21 and an n-In
An n-electrode 22 is formed on the P& plate 11 by vacuum evaporation, and heat removal treatment is performed to bring the electrode into ohmic contact. Thereafter, a cavity length of about 200 to 39 ppm is cut out to complete a buried structure semiconductor laser.

In this example, InP/InGaAsP materials were used, but the present invention is also applicable to other materials, such as td GaAs/GaA
The same can be applied to the lAs group.

Finally, to summarize the life expectancy of the present invention, the active layer does not suffer from mechanical damage during the crystal growth process, thus making it a long-life buried conductor and reducing the yield rate. It's unfortunate that it doesn't work well.

[Brief explanation of drawings]

Figure 1 shows a current confinement mesa substrate buried structure laser (CC
M-LD'). FIG. 2 is a sectional view of a buried conductor laser according to an embodiment of the present invention. In the figure, 1...n, InP substrate, 2...
Projections, 3...Buffer layer 4a and 4b...
・Active layer, 5... First cladding layer, 6...
...Current blocking layer, 7...Second cladding layer, 8.
...Cap layer, 9, curved, P electrode, lO...
...n electrode, 11...n-InP substrate, 12.
... Protrusion, 13 ... Two mutually parallel grooves, 14 ... Flat portion, 15 ... is a buffer layer, 16! I, 16bl16C...
Active layer, 17... First cladding layer, 18...
... Current blocking layer, 19 ... Second cladding layer, 20 ... Cap layer, 21 ... P electrode, 22 ... N electrode be. 4η /(/ grass l figure

Claims (2)

[Claims] (1) A semiconductor substrate having two grooves parallel to each other, an active layer formed on the skeleton semiconductor substrate, and a current blocking layer having a defect in a protrusion between the two grooves,
A semiconductor v-zer characterized in that a region of the nine active layers formed on the protrusion is a growing light emitting region. (2) The semiconductor laser according to claim 1181, characterized in that the active layer has a defect on the side surface of the protrusion.