JPH05190978A - Semiconductor photointegrated element - Google Patents

Abstract

PURPOSE:To make only one time step suffice for crystal growth by a method wherein the conductivity type of the third semiconductor layer and the second semiconductor multilayer film reflector is changed to the second conductivity type so as to form a re-light emitting semiconductor laser while a bipolar transistor is formed in the remaining region. CONSTITUTION:The conductivity type of a p-Al0.4Ga0.6As 26, a p-GaAs/AlAs multilayer film reflector 27 and a p-GaAs 28 is changed downward, from n type to p type by diffusing Zn downward in an n-Al0.25Ga0.75As 19, an n GaAs/ AlAs multilayer film reflector 20 and an n-GaAs 21 only. The interval between upper and lower two multilayer film reflectors 20 and 12 is specified to be 2lambda while a p-InGaAs active layer 16 is to be interposed between the two reflectors 20 and 12 thereby enabling the layer 16 to be positioned on the center of the stationary wave raised in a resonator. Through these procedures, the collector of a bipolar transistor can be connected to one side of a surface light emitting laser by an n-contact electrode 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical integrated device used in optical interconnection and optical computers.

[0002]

2. Description of the Related Art In these applications, an optical functional element having functions such as light emission and light reception, an optical memory and an optical threshold, which is called a smart pixel, is constituted as a minimum unit. As such an optical functional device, a device as shown in FIG. 2 has been reported. A. Details are described in the technical digest of CLEO'91 (CMF7, pp. 46-49) held in the United States in 1991 by Von Lehmen et al. An npn phototransistor is formed on a GaAs substrate, and a surface emitting semiconductor laser having an InGaAs quantum well layer as an active layer is formed on the npn phototransistor. The upper and lower reflecting mirrors of the surface emitting semiconductor laser are made of a semiconductor multilayer film in which GaAs and AlAs are alternately laminated with a thickness of λ / 4 (λ is an oscillation wavelength in the semiconductor). In this device, when light is incident on the phototransistor, a current flows through the surface emitting laser, which causes laser light to be emitted. The laser light goes out to the lower side through the GaAs substrate.

[0003]

The problem with this device is that the device becomes taller in the layer thickness direction. The reflectance of the semiconductor multilayer film reflecting mirror used for the surface emitting laser is required to be 99.9% or so in order to lower the oscillation threshold current of the laser. And for that, many layers of GaAs and AlAs
You have to stack the layers. In the example of FIG. 2, it is about 7 μm only for the surface emitting laser portion. If such a step is formed, it becomes difficult to finely process the lower (photo) transistor. In the layer structure shown in FIG. 2, a transistor may be further formed on the lower side, and thereby a function such as an optical memory which cannot be realized by the element shown in FIG. 2 may be incorporated, but this is not possible because it is difficult to process.

[0004]

The present invention has been made to solve the above problems. The semiconductor optical integrated device according to the present invention comprises a first conductive type first semiconductor multilayer film reflecting mirror, a first conductive type first semiconductor layer, and a second conductive type opposite to the first conductive type on a semiconductor substrate. Of the second semiconductor layer, the third semiconductor layer of the first conductivity type, and the second semiconductor multilayer mirror of the first conductivity type are formed, and the forbidden band width smaller than that in the second semiconductor layer. An active semiconductor layer is formed, and a surface emitting semiconductor laser is formed by changing the second conductivity type of the third semiconductor layer and the second semiconductor multilayer film reflecting mirror in a partial region thereof, and the remaining region is formed. Is characterized in that a bipolar transistor is formed.

[0005]

[Principle] In the present invention, a surface emitting semiconductor laser and a bipolar transistor are formed at spatially different positions. By changing the second conductivity type of the third semiconductor layer and the second semiconductor multilayer film reflecting mirror, a surface emitting semiconductor laser can be formed therein, and a bipolar transistor can be formed in the remaining region. Various functions can be realized by wiring them internally. In such a semiconductor optical integrated device, it is important to form each semiconductor layer by one crystal growth. The method of using the crystal growth twice or more causes various problems during the growth after the second time, which causes a decrease in the yield of the device. Since the application field that requires a very large number of smart pixels is assumed, the crystal growth is 1 from this point.
It is necessary to stay only once. In the present invention, the crystal growth only needs to be done once.

[0006]

1 is a sectional view showing an embodiment of the present invention. Each semiconductor layer is formed on the semi-insulating GaAs substrate 11 by the MBE method. Numeral 12 is a multilayer mirror of n-GaAs / AlAs (24.5 period, doping concentration is 3 × 10 ^18).
The film thickness of cm ⁻³ , GaAs, and AlAs is set to λ / 4. λ is the wavelength inside the semiconductor, and 1 outside the element
μm), 13 is n-Al _0.4 Ga
_0.6 As (doping concentration 3 × 10 ¹⁸ cm ⁻³ , film thickness 0.15 μm), 14 is an n-type graded layer (doping concentration 3 × 10 ¹⁸ cm ⁻³ , film thickness 200 A).
The Al composition x of the n-type graded layer is changed from 0.4 to 0.25 as it goes upward. Base-
This is because the transistor characteristics can be improved by changing the grade between the collector and the collector.
Reference numeral 15 is undoped p ⁻ -Al _0.25 Ga _0.75 As (doping concentration is 10 ¹⁵ cm ⁻³ or less, film thickness is 500 A). In MBE, the undoped layer is p ⁻ and the concentration is 10 ¹⁵ cm
^-3 or less.

Reference numeral 16 is an undoped p ^-- InGaAs active layer (thickness is 100 A), and 17 is an undoped p ^-- A.
l _0.25 Ga _0.75 As (film thickness is 500 A), 18 is p-A
l _{0. 25} Ga _0.75 As (doping concentration 1x10 ¹⁹ cm
^-3 , film thickness 100 A), 19 is n-Al _0.4 Ga _0.6 A
s (doping concentration is 3 × 10 ¹⁸ cm ⁻³ , film thickness is 0.1
5 μm), 20 is an n-GaAs / AlAs multilayer mirror (15 cycles, doping concentration is 3 × 10 ¹⁸ cm ⁻³ , Ga
The film thickness of As and AlAs is set to λ / 4. λ is a wavelength inside the semiconductor, and is set to 1 μm outside the element), 21 is n-GaAs (doping concentration is 1 × 10 ¹⁹ cm ⁻³ , film thickness is 1000 A), 22, 24
Is an n-contact electrode made of AuGe-Ni.
23 and 25 are p-contact electrodes.

26 is p-Al _0.4 Ga _0.6 As, 27 is p-GaAs / AlAs multilayer film reflecting mirror, 28 is p-Ga.
As, but these are the original n-Al _0.25 Ga _0.75 A
s19, n-GaAs / AlAs multilayer mirror 20, n
The conductivity type is converted from the n-type to the p-type by diffusing Zn from the upper side only in the -GaAs 21.

The interval between the upper and lower two multilayer film reflecting mirrors is 2λ and p
^- -InGaAs active layer 16 are to come in between. This allows the p ⁻ -InGaAs active layer 16 to be placed at the antinode of the standing wave standing in the resonator.

The emitter of the bipolar transistor is 5μ
m-square, collector is 25μm-square and current gain is about 100
Is. The surface emitting laser has a diameter of 10 μm. The oscillation wavelength is 1 μm and the threshold current is about 1 mA. Since the collector of the bipolar transistor and the (-) side of the surface emitting laser are connected by the n-contact electrode 24, the equivalent circuit has the same configuration as that of FIG. The height of the device is the same as that of the bipolar transistor and the surface emitting laser, and the problem as in the past does not occur. Therefore, a fine process of several μm is possible.

[0011]

EFFECTS OF THE INVENTION According to the present invention, there is no need for a process where there is a large step, and a wafer such as a surface emitting semiconductor laser and a bipolar transistor can be formed by one growth, and by connecting them internally variously. Various optical functional devices can be realized. In the embodiment, the GaAs-based material has been described, but other InP-based materials can of course be applied.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a conventional example.

[Explanation of symbols]

11 semi-insulating GaAs substrate 12 n-GaAs / AlAs multilayer film reflective mirror 13 n-Al _0.4 Ga _0.6 As 14 n-type graded layer 15 p ^{− −} Al _0.25 Ga _0.75 As 16 p ^{− −} InGaAs active layer 17 p ⁻ − Al _0.25 Ga _0.75 As 18 p-Al _0.25 Ga _0.75 As 19 n-Al _0.4 Ga _0.6 As 20 n-GaAs / AlAs multilayer mirror 21 n-GaAs 22, 24 n-contact electrode 23, 25 p-contact electrode 26 p-Al _0.4 Ga _0.6 As 27 p-GaAs / AlAs multilayer film reflecting mirror 28 p-GaAs

Claims (1)

[Claims] 1. A first semiconductor multilayer mirror of a first conductivity type on a semiconductor substrate, a first semiconductor layer of a first conductivity type, and a second semiconductor of a second conductivity type opposite to the first conductivity type. Layer, a third semiconductor layer of the first conductivity type, and a second semiconductor multilayer film mirror of the first conductivity type are formed, and an active semiconductor layer having a smaller forbidden band width than the second semiconductor layer is formed in the second semiconductor layer. Has been formed,
A surface emitting semiconductor laser is formed by changing the third semiconductor layer and the second semiconductor multilayer film reflecting mirror to the second conductivity type in some of these regions, and a bipolar transistor is formed in the remaining region. A semiconductor optical integrated device characterized by: