Abstract

We present a new GaAs integrated optoelectronic neuron for use in neural networks. We have previously demonstrated that the integration of photodetectors, thresholding transistors, and a light source on a single substrate allows one to have high neuron density with acceptable power dissipation. In this paper we report a circuit in which we used a double heterostructure LED (light emitting diode) as the light source. We use an LED rather than laser diodes because LEDs can be operated with small currents, due to the lack of a threshold current. To minimize the total mesa height and maintain high LED quantum efficiency, MSM (metal–semiconductor–metal) photodetectors were used. The thresholding transistor was a MESFET (metal–semiconductor field-effect transistor). The total mesa height is less than 3 μm. Since no two devices share an epitaxial layer, each device is individually optimized. Our circuit uses two photodetectors, one to set the threshold voltage and the other to detect the signal. With this circuit, we can also build both excitatory and inhibitory neurons. Results from our experimental studies are presented.

© 1991 Optical Society of America