JPH01239967A - Semiconductor device - Google Patents

Abstract

PURPOSE:To effectively reduce an irregularity in photodetecting brightness by a method wherein a light-emitting element and a photodetector, both composed of a compound semiconductor layer, are formed on an Si substrate to be adjacent to each other, a MOSFET formed to be adjacent to them is used and an optical output of the photodetector is controlled to be constant by using an output signal from the photodetector. CONSTITUTION:Compound semiconductor layers are formed on an Si substrate by an epitaxial growth method; a light-emitting element 201 such as an LED or the like and a photodetector 202 such as a photodiode or the like are made up of the layers. These elements comprise a P-N junctions of the compound semiconductor; voltages are applied in the forward direction in the element 201 and in the reverse direction in the element 202. The light-emitting element and the photodetector are constituted in this manner; a beam of light emitted from the element 201 by a drive current I from a MOSFET element 203 formed to be adjacent to the element 201 is detected by using the element 202; a photoelectric current Ip corresponding to the light intensity is applied to the element 203; the drive current I is controlled in such a way that the Ip becomes constant. By this setup, an optical output becomes stable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a semiconductor device. In particular, light emitting diodes (
The present invention relates to an optoelectronic integrated circuit on a silicon substrate suitable as an LED (LED) array.

[Prior Art 1] Light emitting diodes (LEDs) have been applied to various fields as small and lightweight light sources. In particular, LED arrays in which a plurality of LEDs are arranged in one dimension are expected to develop as light sources for high-speed, high-resolution page printers.

Conventional LEDs emit light by epitaxially growing a single crystal thin film such as an aluminum gallium arsenide (AI2GaAs) layer or a GaAs layer on a gallium arsenide (GaAs) substrate, and passing a forward current through the Pn junction formed by these layers. I was getting .

If a plurality of these LEDs are arranged, it becomes an LED array.

[Problem to be solved by the invention 1 However, the above-mentioned conventional technology has the drawback that the characteristics (especially brightness) of LEDs vary widely due to the GaAs-based treatment and crystal defects contained in the epitaxial film, and there are large individual differences. Was. Particularly in LED arrays, a plurality of integrated LEDs are required to have uniform characteristics, and variation in brightness is a fatal problem.

The present invention is intended to solve these problems, and its purpose is to provide a semiconductor device with extremely small variations in luminance.

[Means for Solving the Problems] A semiconductor device of the present invention includes a light emitting element made of a compound semiconductor layer provided on a silicon substrate, and a compound semiconductor layer also provided on the silicon substrate. The device is characterized by comprising an adjacent light receiving element and a drive circuit in the silicon substrate having a function of controlling the light output of the light emitting element to a constant level based on an output signal from the light receiving element.

[Implementation Example 1] Hereinafter, the present invention will be described in detail based on Examples.

FIG. 2 shows a basic configuration diagram of a semiconductor device according to the present invention.

The semiconductor device of the present invention consists of three monolithically integrated basic elements. A light emitting element (LE) is provided on a compound semiconductor layer epitaxially grown on a silicon substrate.
D nato) 201.

Similarly, a light receiving element (such as an odd diode) 202 provided in a compound semiconductor layer epitaxially grown on a silicon substrate, and a drive circuit 2 provided in the silicon substrate.
It is 03. Both the light-emitting element and the light-receiving element are composed of Pn junctions of compound semiconductors formed at the same time, and the difference is that the voltage is applied in the forward direction for the light-emitting element and in the opposite direction for the light-receiving element. These two elements are adjacent to each other on the silicon substrate. The light receiving element detects the light emitted by the light emitting element due to the drive current I flowing out from the drive circuit, and transmits a photocurrent Ip corresponding to the intensity of the light to the drive circuit. The drive circuit controls the drive current I so that Ip remains constant, and can always obtain stable optical output. A specific driving circuit is an APC (A
This is similar to the auto...aticPower ConLroll) circuit.

FIG. 1 shows a cross-sectional structural diagram of a semiconductor device according to the present invention.

MOS used for the drive circuit in the p-Si substrate 101
FET is provided. On the silicon surface, a double heterostructure light emitting element (LED, semiconductor laser, etc.) and light receiving element ( ) are provided. These light-emitting elements and light-receiving elements basically have the same structure and are formed at the same time, but the - voltage application direction is Pn for the light-emitting element.
The difference is that the light receiving element is wired in the opposite direction to the forward direction of the junction. Therefore, in order from the silicon surface side, the n-GaAs buffer layer 102, the n A Qo
, z Gao, y A S cladding layer 103, GaA
s active layer 104. p-Al1. o 3(J ao,
tAS cladding layer 105. A p-GaAs contact layer 106 is epitaxially grown. Although there are various growth methods, a metal organic chemical vapor deposition method (MOCVD method) or a molecular beam epitaxial method (MBE method) is suitable. Further, the p-side electrode 107 of the light emitting element is connected to the p-side electrode of the light receiving element. Silicon substrate 101 and G
In order to prevent leakage current between the a A s layer lO2,
It is sufficient to apply an appropriate voltage to the silicon substrate so that both potentials are equalized or reverse biased. The manufacturing method is to first create MOS F using the normal process.
Explosive ET. The drive circuit is CMOS (complementary MO3
) or a bipolar transistor. Each device is isolated by SiO2108. Thereafter, GaAs or AρGaAs is epitaxially grown continuously to form a light emitting element and a light receiving element. After depositing an insulating film (StO2, SiN, etc.) 110 on the entire surface, metal wiring is completed. In order to obtain ohmic contact, it is desirable to use different materials for the Si-based metal wiring and the GaAs-based metal wiring. Af2 or Af2-5i or Af;! to Si system. , -51-
Aff-based metal illumination such as Cn is suitable. GaA
Cr/N i / A 11 to the s system.

Au-based metals 112 such as Ni/Ge/Au and Cr/Au are suitable. Therefore, the wiring between devices is
This is done by contacting Af2-based and Au-based metals.

FIG. 3 is a graph showing the relationship between the driving current of the LED and the luminous intensity. As mentioned above, there are large individual differences in the characteristics of LEDs, and there are variations in characteristics such as 301, 302, and 303. Conventionally, in order to keep the drive current I constant, each characteristic
The luminescence intensity varies depending on the surname: Pl, p, and p2. However, according to the present invention described above, the light intensity is detected by a photodiode, and the drive current is adjusted to 11.
1 and I2, the desired light intensity P can be stably obtained with any LED of any characteristic.

FIG. 4 is a block diagram of a semiconductor device according to the present invention configured as an array of light emitting elements such as LEDs and semiconductor lasers. The basic configuration of the drive circuit 403, light emitting element 404, and photodiode 405 plus a MOS switch 406 constitutes one unit, and a desired number of units are arranged one-dimensionally. The shift register array 401 sequentially transfers start pulse (SP) signals, which are sequentially fetched into the latch array 402 along with data (D) indicating whether the light emitting element emits light or does not emit light. When the light emission data is captured, the gate of the MOS switch 406 is opened to cause the light emitting element to emit light until the next data is rewritten. Since the light emitting element array configured in this manner can maintain constant emission intensity for each bit, the uniformity of the overall brightness can be extremely improved. shift register column 401,
Latch row 402, drive circuit 403, MOS switch 40
It goes without saying that 6 can eventually be integrated within the same silicon substrate.

[Effects of the Invention] The present invention has the following excellent features. First of all, the light intensity of one light emitting element can be stably maintained at a constant value. Not only can the same brightness be obtained even if there are variations in the characteristics of the light emitting elements, but also constant light intensity can be obtained even if the environmental conditions (for example, temperature) change. This feature is particularly noticeable when a plurality of light emitting elements are integrated, such as in an LED array.

Second, since a desired luminance can be obtained in principle with a light emitting element having any characteristics, the occurrence of defects is extremely reduced, which is advantageous for improving yield and reducing costs. This is particularly effective for LED arrays, as even a single LED cannot be defective.

Third, since a silicon substrate is used, it is advantageous for heat dissipation. The thermal conductivity of a silicon substrate is approximately twice as high as that of a GaAs substrate, making it suitable for devices that handle large currents, such as light emitting devices. This is particularly effective in applications such as LED arrays where multiple light emitting elements are integrated and power consumption is large.

Fourthly, it is possible to prevent the emitted light intensity of the light emitting element from changing over time. Generally, when a light-emitting element continues to emit light by current injection, crystal defects increase over an hour and the light intensity decreases, but in the present invention, when the light intensity decreases, the drive current is automatically increased and kept constant. brightness can be ensured. In particular, a compound semiconductor layer epitaxially grown on a silicon substrate initially contains many crystal defects due to mismatched lattice constants. Therefore, a light emitting element on a silicon substrate must have the structure of the present invention.

Brightness deteriorates extremely quickly. In other words, it can be said that the present invention has a unique effect in realizing a light emitting element on a silicon substrate.

Fifth, since all the necessary circuits can be integrated within the silicon substrate, the number of external connection terminals is small and implementation is easy. Conventional LED arrays have 2,000 to 4
000 wire pondage jigs were required,
According to the present invention, only about 10 wires need to be bonded.

Sixth, since the light-emitting element and the light-receiving element are manufactured by the same process, the process is simplified and zero yield is improved and costs are reduced. This is because structurally the same element has the functions of a light emitting element and a light receiving element by changing the direction of voltage application.

Seventh, since the light emitting element and the light receiving element are adjacent in a plane,
The present invention can also be applied to a case where the light emitting element is a semiconductor laser. Light emitting diodes emit light in all directions, so
Although the light-receiving element can receive light no matter where it is placed, in the case of a semiconductor laser, it emits light only in the horizontal direction, so the light-emitting element and the light-receiving element cannot be adjacent to each other in a plane as in the present invention. is important. This makes it possible to realize a semiconductor laser array with constant light intensity.
He made significant contributions to speeding up laser beam printers and laser address displays.

As described above, the present invention has many excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional structural diagram of a semiconductor device according to the present invention, FIG. 2 is a basic configuration diagram of a semiconductor device according to the present invention, FIG. 3 is a graph showing the relationship between drive current of a light emitting element and light emission intensity, and FIG. FIG. 2 is a block diagram of a semiconductor device of the present invention configured as a light emitting element array. Applicant: Seiko Epson Co., Ltd. Agent Patent Attorney Mogami (1 other person) MO, s P
ET e尤, *”r 'a-i='kekuzu 1 drawing + L f engineering drive? p electric 5 ( 蒲 3 drawing

Claims (1)

[Claims] a light-emitting element made of a compound semiconductor layer provided on a silicon substrate; a light-receiving element adjacent to the light-emitting element made of a compound semiconductor layer also provided on the silicon substrate;
A semiconductor device comprising a drive circuit in the silicon substrate that has a function of controlling the light output of the light emitting element to a constant level based on an output signal from the light receiving element.