JPH0827674B2 - Optical neurochip - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical neurochip which is one of optical devices used in a neurocomputer which imitates the information processing capability of the brain of an organism.

[Conventional technology]

A neurocomputer is a massively parallel computer with a learning ability that focuses on the wiring pattern (temporal / spatial pattern of the coupling strength between neurons) of a network composed of many neurons (neurons).
It has potential processing capabilities that current computers are not good at, such as pattern recognition and associative functions for voice, handwritten characters, and images.

A conventional example of an optical neurochip used in such a neurocomputer is shown in FIG. Figure 3 shows, for example, IEICE Technical Report CPSY, V
FIG. 5 is a conceptual diagram of a conventional optical neurochip described in ol, 88, No. 107 (1988), pages 53-60. In the figure, 1 is, for example, G _a
AlG _a mounted on the A _s substrate 4, _a light emitting layer composed of the As light emitting element array 1 a based on A _s , 2 is AlG _a mounted on the light emitting layer 1 through an optically transparent electrically insulating layer 5. spatial modulation layer consisting of A _s base MQW use spatial light modulator 2a, 3 is an electrically insulating layer 5
This is _a light-receiving layer composed of a G _a A _s- based line-shaped light-receiving element array 3a mounted on the spatial modulation layer 2 via.

Next, the operation will be described. When a current is passed between the electrodes of the light emitting element array 1a of the optical neurochip, a light output is generated in the substrate 4 in the vertical direction. This optical output is V _i (i = 1,2 ..., N;
N is the number of neurons, and here is the number of light emitting elements of the light emitting element array 1a). This optical output V _i is the inter-synaptic coupling strength T _ij (i = 1,2) in the neural network model.
, N, j = 1, 2, ..., N) is detected as a photocurrent U _j (j = 1, 2, ..., N) in the light receiving element array 3a through the spatial light modulator 2a. That is, Therefore, the connection between neurons can be performed in the chip. In order to change this coupling strength, it is necessary to externally control the light transmittance of the spatial light modulator 2a for each pixel.

[Problems to be Solved by the Invention]

Since the conventional optical neurochip is configured as described above, it is necessary to integrate the spatial light modulation element between the light emitting element array and the light receiving element array and to integrate the light emitting layer and the spatial modulation element. There is a problem that alignment between the layers and the light-receiving layer is required, which complicates manufacturing and makes it difficult to reduce the cost.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical neurochip capable of simplifying manufacturing and reducing the cost.

[Means for solving the problem]

The optical neurochip according to the present invention comprises a light emitting layer 1 composed of a light emitting element array 1a mounted on a substrate 4, and a light receiving layer mounted on the light emitting layer 1 with an optically transparent electrical insulating layer 5 interposed therebetween. The light receiving layer 3 including the element array 3b, and the light receiving control element in which the photoelectric conversion efficiency is modulated by applying a voltage or the voltage control element in which the photoelectric conversion efficiency is modulated by applying a voltage to the light receiving element array 3b. It is characterized in that it is configured by using a light receiving element to which the above are connected.

[Action]

The light emitting element array 1a of the light emitting layer 1 emits light upward with respect to the substrate 4. The light receiving element array 3b of the light receiving layer 3 receives the light and outputs a photocurrent as an electric signal, which is controlled from the outside. This control is performed by a signal applied to the control terminal of the light-receiving control element when the light-emitting element array 1a is configured by the light-receiving control element, and is configured by connecting a voltage control element or the like to the light-emitting element array 1a. In the case of doing, it is performed by the signal given to this control element.

Example of Invention

FIG. 1 is a conceptual diagram of an optical neurochip according to an embodiment of the present invention. In FIG, 1 is a light emitting layer made of, for example, G _a A _s substrate (semiconductor substrate) 4 AlGaAs mounted on _a A _s based linear emitting element arrays 1a, 3 is transparent to optical on the light-emitting layer 1 Photodetector array mounted via electrical insulation layer 5
This is a light-receiving layer made of 3b. The light receiving element array 3b is, for example, ME.
It can be realized by an S (metal semiconductor) field effect transistor (light reception control element), and the photocurrent can be controlled by a signal given to the light reception sensitivity control electrode (control electrode) 3c.

FIG. 2 is a sectional view showing the layer structure of the light receiving element (light receiving layer 3) which constitutes the light receiving element array 3b of FIG. This figure 2
In FIG. 4, reference numeral 4a denotes a substrate on which the light receiving elements that form the light receiving element array 3b are mounted, and is provided with a hole for transmitting the light Vi emitted from the light emitting element, or made of a material that transmits the light Vi. Is. 6 is a Bragg reflection layer, 7 is a channel layer (n type), 8 is a depletion layer, 9 is a source electrode, 10 is a drain electrode, and 11 is the electrical insulating layer 5 shown in FIG.
It is a transparent gate electrode that receives the light Vi that has been transmitted through.

Next, the operation will be described. For example, the light V _i (i = 1, 1) emitted from the i-th light-emitting element that constitutes the light-emitting element array 1a
2 ..., N) are incident on the j-th light receiving element forming the light receiving element array 3b. At this time, if the voltage to the control electrode 3c of the j-th light receiving element is V, the quantum efficiency η of this j-th light receiving element is
Is expressed by the following equation.

Here, R is the reflectance, α is the absorption coefficient, and L _P is the hole extension length (the majority carriers are electrons). W is a depletion layer thickness, which is given by the following equation.

Here, ε _S is the dielectric constant, q is the charge, N _D is the donor density, V _bi is the built-in voltage, k is the Boltzmann constant, and T is the absolute temperature. From the above equations (1) and (2), the quantum efficiency η becomes a function of the voltage V, Take a gap. That is, this embodiment can modulate the photoelectric conversion efficiency and can replace the conventional spatial light modulator. In addition, I _{ph in} FIG. 2 represents a photocurrent.

Further, the light that has passed through the Bragg reflection layer 6 and reached the channel layer 7 is reflected by the channel layer 7 and is not photoelectrically converted, and is reflected by the Bragg reflection layer 6 to irradiate the channel layer 7 again. Therefore, the photoelectric conversion efficiency is improved.

As described above, each light receiving element of the light receiving element array 3b in the above-described embodiment is designated at each point on the two-dimensional lattice on the light receiving layer 3 by means of a well-known technique not shown here, and each light receiving element is designated. The photosensitivity can be adjusted by the voltage V applied to the control electrode 3c connected to the control electrode 3c, and thus the inter-neuron coupling strength can be changed without the conventional spatial modulator.

In the above embodiment, the MES / FET is used as the light receiving element array.
However, the present invention is not limited to this and may be a light receiving element such as a phototransistor provided with an external control electrode. Further, in the above embodiment, the light receiving control element such as the phototransistor is used as the light receiving element array, but other devices (elements) capable of photoelectric conversion can be used, and the specifications of each light receiving element can be used. A voltage control element or the like, such as a combination of a voltage control type resistor and a capacitor, or a combination of a resistance and a voltage control type capacitor, or a voltage control type resistor, a voltage control type capacitor, etc. It is used to connect in series or in parallel to the light receiving element array so that this light receiving element array operates optimally. That is, the light receiving element may be used so that the photocurrent is controlled by the control element such as the resistor connected to the outside of the light receiving element array. Furthermore, in the above embodiment, the case of application to a neural network model has been described, but it may be applied to an optical converter, a switching matrix device, or the like.

〔The invention's effect〕

As described above, according to the present invention, with respect to the light receiving element array, a light receiving element whose photoelectric conversion efficiency is modulated by applying a voltage or a voltage control element whose photoelectric conversion efficiency is modulated by applying a voltage is connected. Since it is configured using a light-receiving element, the photoelectric conversion efficiency of the light-receiving element can be controlled from outside the light-receiving element array (outside the optical neurochip), which allows integration including conventional spatial light modulators. Therefore, it is possible to obtain the effects of simplifying the manufacturing and reducing the cost.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an optical neurochip according to an embodiment of the present invention, FIG. 2 is a sectional view showing a structure of a light receiving element in this embodiment, and FIG. 3 is a conceptual diagram of a conventional optical neurochip. . 1 ... Light emitting layer, 1a ... Light emitting element array, 3 ... Light emitting layer,
3b ... Photodetector array, 3c ... Control electrode, 4 ... Substrate,
5: Electrical insulating layer.

Claims (1)

[Claims] 1. A light emitting layer comprising a light emitting element array mounted on a substrate, and a light receiving layer comprising a light receiving element array mounted on the light emitting layer via an optically transparent electrical insulating layer. In the optical neurochip, a light-receiving control element in which photoelectric conversion efficiency is modulated by applying a voltage or a voltage-controlled resistor or voltage-controlled capacitor in which photoelectric conversion efficiency is modulated is connected to the above light-receiving element array. An optical neurochip characterized by being configured using elements.