JPS62173779A - Optical integrated circuit device - Google Patents

Abstract

PURPOSE:To alleviate an adverse influence of a dislocation or a defect in a substrate to a laser by forming a recess at a position of the substrate to form the laser, and burying the recess with a conductive GaAs to form a buffer layer. CONSTITUTION:A recess is formed on a semi-insulating substrate 1, and the recess is buried with a P-type GaAs by an epitaxially growing method to form a buffer layer 2. The layer 2 alleviates an adverse influence of a dislocation or a defect in the substrate 1 to the layer units 2-8. The alleviating effect can be increased by deepening the recess. many FETs 20 are composed on the substrate 1 in addition to the lasers 2-8. In this case, the lasers 2-8 and the FETs 20 are formed on the same surface irrespective of the depth of the recess. Accordingly, a problem of wiring stepwise difference due to the increased thickness of the buffer layer does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical integrated circuit, such as a light emitting source in optical communication, which changes its optical output depending on an input electrical signal.

BACKGROUND OF THE INVENTION The so-called BTR8 type semiconductor laser is known to have excellent performance and high reliability. Therefore, conductive G
a This BTR8 type semiconductor laser and FE are mounted on the A s substrate.
The present applicant has already proposed an optical integrated circuit device that integrates T.

Problems to be Solved by the Invention However, when a large number of FETs are fabricated on a conductive GaAs substrate, the stray wires between the FETs are more likely to occur than on a semi-insulating GaAs substrate. As the capacity increases, the resulting delay becomes a problem.

Therefore, in the present invention, the FET takes advantage of the characteristics of the semi-insulating substrate to reduce the stray wire capacitance between the FETs, and the laser is designed to avoid being affected by the semi-insulating substrate, which generally has many dislocations and defects, as much as possible. The aim is to realize a high-performance, highly reliable optical integrated circuit on a semi-insulating substrate by creating a structure that does not significantly affect the characteristics of the laser.

Means for Solving the Problem The technical means of the present invention for solving this problem is to create a recess on the substrate at the location where the laser is to be manufactured, and to fill the recess with conductive GaAs. .

Function: This conductive GaAs is produced by epitaxial growth technology, so it is a relatively good crystal, which alleviates the adverse effects on the laser such as dislocations and defects in the semi-insulating substrate (
The so-called pie) 1 layer). By increasing the depth of this recess, the thickness of the buffer layer can be increased, and the relaxation effect can be further increased. On the other hand, since the laser and FET are fabricated on the same surface regardless of the depth of the recess, there is no problem with the wiring step difference due to the thicker buffer layer.

Embodiment FIG. 1 is a sectional view of an optical integrated circuit according to an embodiment of the present invention, in which a blocking layer growth layer 9 was used as the FET active layer. Reference numerals 2 to 8 in FIG. 1 indicate the aforementioned BTR8 type semiconductor laser, in which there is a current blocking layer 3 having two ridges on the p-type GaAs growth layer 2, and current can be injected only through the gap between the edges. It is possible. Therefore, current is concentrated in the portion directly above the ridges of the active layer 5, and laser oscillation occurs at a low threshold. The p-type GaAs growth layer 2 also serves as a buffer layer that alleviates the influence of dislocations and defects on the laser of the semi-insulating GaAs substrate 1, and by increasing its depth, dislocations and defects can be reduced. The effects of defects are more relaxed.

On the other hand, an FET in which the current blocking layer growth layer 3 is the active layer 9 is a MESFET when the gate electrode 11 is made of metal.
, p-type AlGaAs, it becomes a heterojunction FET. The p-type GaAs2 and the p-type electrode 13 are in ohmic contact, p
Since the mold electrode 13 and the source electrode 12 are in metal-to-metal contact, the laser and the FET are connected in series. Therefore, the current flowing through the laser and the resulting laser output light can be modulated by the gate input signal S of the FET.

The manufacturing method of this optical integrated circuit will be briefly described. First, a recess is formed in the semi-insulating GaAs substrate 1 by chemical etching (FIG. 2(a)). Next, by epitaxial technology, the recess is filled with a p-type GaAs growth layer 2 (see figure (b).
)). Furthermore, p-type GaA
After attaching a mask to the mesa part of s2, the FET explosion point is
Etch until the semi-insulating substrate 1 is obtained (see figure (C)
)). Next, an n-type GaAs blocking layer 3 is grown. and two parallel ridges (height 1.5μ
m9 width: 2011 m, width between ridges: 6 μm). On top of this, p-type AlGaAs first cladding layer 4 (thickness 0
．． 4 μm), A I Ga Ats active layer 4 (thickness 0.03 to 0.04 μm), n-type AI GaAs second cladding layer 5 (thickness 2 μm), n-type Ga As cap layer 7 (thickness 2.5μm).Next, FET
By selectively etching only the fabricated portion, the n-type GaAs layer 9
0 surface is exposed. Next, the n-type GaA3 blocking layer and the FET active layer 9 are separated by etching. Next, a p-type electrode 13 and an n-type electrode 10.12 are formed by vapor deposition. Finally, a gate electrode 11 is formed.

Effects of the Invention The present invention provides a buffer layer between the semiconductor laser growth layer and the semi-insulating substrate to prevent the influence of dislocations and defects in the substrate and to integrate a good semiconductor laser. Furthermore, since a semi-insulating substrate is used, a large number of FETs can be integrated, and the FET active layer also serves as the laser's current blocking layer, second cladding layer, or cap layer. , is an optical integrated circuit characterized by easy fabrication. Also, 60℃, 5 m
In the life test of 'W, there was almost no difference from a general BTR3 type semiconductor laser, and the operating characteristics of the FET section were the same as a general GaAs IC. In this way, the influence that this optical integrated circuit has on the integration of semiconductor lasers and GaAs ICs, and on optical communication relationships is significant.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an optical integrated circuit device according to an embodiment of the present invention, and FIGS. 2(a) to (C) are cross-sectional views showing a part of the manufacturing process of this optical integrated circuit device. 1... Semi-insulating G a A g substrate, 2...
...p-type GaAs buffer layer 3...
・N-type GaAs blocking layer, 4...
p-type AlGaAs first cladding layer, 6...AI
G a As active layer, 6...n-type A I
G a A g second cladding field, 7...n-type G
aAs cap layer, 8...n-type electrode, 9...
... n-type GaAsFET active layer, 1o ... drain electrode, 11 ... gate electrode, 12 ...
. . . Source electrode, 13 . . . P-type electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
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Claims (3)

[Claims] (1) Conductive Ga on a part of the surface of the semi-insulating GaAs substrate
An As buried layer is formed, a semiconductor laser is formed on the surface of the conductive GaAs buried layer, and a FET is formed on the surface of the semi-insulating GaAs substrate, and a current flowing through the semiconductor laser is caused by the FET. An optical integrated circuit device characterized in that it is modulated. (2) A semiconductor laser has a current blocking layer, a first cladding layer, an active layer, a second cladding layer, and a cap layer formed in this order on a conductive GaAs buried layer, and two layers are formed on the blocking layer. 2. The optical integrated circuit device according to claim 1, wherein the optical integrated circuit device has a structure in which two ridges are provided and current can be injected only through the gap between the two ridges. (3) The optical integrated circuit device according to claim 2, wherein the current blocking layer, the second cladding layer, or the cap layer constitutes an FET active layer.