Operation characteristics of exciton absorption reflection switch arrays

Abstract

The exciton absorption reflection switch array (EARS) made of a GaAs/AlGaAs multiple quantum well (MQW) modulator and a GaAs heterojunction phototransistor (HPT) coupled by a distributed Bragg reflector (DBR) functions as an optical three-terminal device with a high contrast ratio and a high optical gain. In this paper, it is shown that an OR gate can be constructed by connecting the MQW modulator and an HPT electrically in parallel while an NOR gate can be made by a series connection. The optical gain and the response time at each gate are measured and the results are found to coincide with the predictions from the equivalent circuit model. Especially, it is found that the response time can be reduced substantially if a resistor is connected in parallel to the MQW modulator in the NOR gate. The switching energy of the EARS is 3.8 fJ/μm2. Hence, a switching on the subnanosecond level is possible if the device size is reduced to about 10 μm.