JPS60260178A - Optical integrated circuit device - Google Patents

Abstract

PURPOSE:To form an optical integrated circuit having an inverter, to be turned to the base of a digital circuit, composed of a photo element by a method wherein an element to be used to detect a light and a light-emitting element are integrated in the state of parallel connection on a semiconductor substrate. CONSTITUTION:A light-emitting element 7 and a light-receiving element 8 are connected in parallel. When a terminal 21 is plus-biased and a terminal 22 is minus-biased, a current runs on the active layer 13 of a semiconductor laser, and a laser oscillation is generated. A photo conductive element, which is a light- receiving part 18, is connected to the semiconductor laser in parallel, but when no photo signal is inputted from outside, no current runs because the light-receiving part 18 is in the state of high resistance. Then, when a photo signal is inputted, the resistance of a high resistance layer is reduced as it is absorbed by the light-receiving part 18. As a result, a part of the current running to the semiconductor laser runs to the light-receiving part, the current running to the semiconductor laser is attenuated, and the photo output is decreased. The oscillation of the semiconductor laser can be stopped by working out the design of this device in such a manner that the voltage running on the semiconductor laser is reduced to the threshold voltage or below by the input of photo signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical integrated circuit used in a logic circuit.

(Structure of conventional example and its problems) In recent years, research and development of optical devices has progressed, and attempts have been made to integrate individual semiconductor lasers, photodetectors, etc. with electronic devices. This aims to miniaturize the transmitting and receiving sections in optical communications.

The most typical conventional example is a device in which a semiconductor laser and a transistor or field effect transistor (FgT) are monolithically integrated.

Figure 1 shows its basic circuit.

In Figure 1, 1 is a resistor, 2 is a semiconductor laser, and 3 is an FE.
T, 4.5 indicates a terminal, and by inputting a modulation signal to the gate 6 of the FET 3, an optical signal is extracted from the semiconductor laser 2. In contrast to analog elements, research and development of integrated circuits in which digital circuits essential to logic circuits are constructed using optical elements is desired. Optical digital circuits lay the foundation for realizing optical computers.

(Objective of the Invention) In view of the above circumstances, the present invention provides an optical integrated circuit in which an inverter, which is the basis of a digital circuit, is constituted by an optical element.

(Structure of the invention) The invention has an integrated structure. With this configuration, when the input optical signal is at a low level, the resistance at both ends of the photodetector is high;
The current flows to the light emitting element side and outputs a high-level optical signal as an output. Furthermore, when the input optical signal is high, the resistance at both ends of the light-receiving element decreases, and the current on the light-emitting element side decreases, so that a low-level optical signal is obtained.

(Description of Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a basic circuit of the present invention, in which a light emitting element 7 and a light receiving element 8 are connected in parallel. Figure 3(a),'
(b) shows an embodiment of an optical integrated circuit using a semiconductor laser as a light emitting element and seven otoconductive elements as a light receiving element. That is, first, on the n-GaAs substrate 11 and on the p-G
a2At1-2As layer 16, n-GazAtl-2A
A buried laser is formed by the S layer 17 (FIG. 3(a)), and then the p-layer which is the buried layer is formed.
GazA! -1-ZAsAs layer, n-Ga2fit+
- A part of the 2As layer 17 is removed and high resistance Ga is applied to that part.
A wAt1-wAs layer 18 is grown to cover the surface and substrate 1.
1 side heomic electrodes 19 and 20 are formed (Fig. 3 (
b)). The operation of the optical integrated circuit element configured as described above will be explained below. When terminal 21 is biased positively and terminal 22 is biased negatively, current flows through the active layer 13 of the semiconductor laser, causing laser oscillation. As mentioned above, the photoconductive element, which is the light receiving section (18), is connected in parallel with the semiconductor laser, but if no optical signal is input from the outside, the light receiving section (18) has a high resistance, so no current flows. . Next, when an optical signal is input, it is absorbed by the light receiving section (18), so that the resistance of the high resistance layer decreases. For this reason, part of the current flowing through the semiconductor laser flows into the light receiving section, and the current flowing between the semiconductor and the laser decreases.
Light output decreases. The oscillation of the semiconductor laser can be stopped by designing the semiconductor laser so that the current flowing through the semiconductor laser upon input of an optical signal is reduced below the threshold current. This device operates as an optical inverter, and its characteristics are shown in FIG. By using a semiconductor laser, the change in optical output can be made steeper.

Note that although a buried semiconductor laser is used as the light emitting element in this embodiment, a semiconductor laser of any structure can be used. In addition, not only GaAs-based and GaAlAs-based lasers (InP-based and other semiconductors can also be used. Furthermore, as a light receiving element, GaAs or Ga
Although an AtAs photoconductive element is used, other materials can be used, and the material can be selected depending on the wavelength of the light to be detected. It is still possible to integrate a light receiving element other than a photoconductive element as a light receiving element, and it is also possible to connect a resistor to the light receiving element.

As described above, the present invention can exhibit the characteristics of an inverter by using an integrated circuit device in which at least an element for detecting a source and a light emitting element are connected in parallel, and its practical effects are significant.

[Brief explanation of drawings]

FIG. 1 is a basic FET integrated circuit of a conventional example, FIG. 2 is a basic circuit of the present invention, and FIGS. 3 (a) and (b) are cross-sectional views of an element that integrates a semiconductor laser and a light receiving element. FIG. 4 is a characteristic diagram of the integrated circuit. 1...Resistance, 2,7...Semiconductor laser, 3...FE
T. 4.5,6,9.10121.22... terminal, 8...
・Photodetector, 11-n-GaAs substrate, 12-n-G
axAZl-xAs cladding layer, 13-Ga2A71
-yAs active layer, 14...p-GaxAtl-xA
S cladding layer, 15-p-GaAs layer, 16-p-
Ga2A71-2As layer, 17...n-Ga, LAt
l-2As layer, 18...High resistance Ga,, A71-A
s layer, 19, 20--ohmic electrode. (O≦W≦/kuχ, )J, Z). Figure 1 Figure 2 Figure 3 (a) (b) 4th 9th input

Claims (1)

[Claims] An optical integrated circuit device characterized in that at least a light-detecting element and a light-emitting element are integrated in parallel connection on a semiconductor substrate.