Current self-oscillations in photoexcited type-II GaAs-AlAs superlattices

Self-oscillations of the photocurrent have been observed in type-II GaAs-AlAs superlattices. In addition to the fundamental frequency, several higher harmonics are present. The frequency of the oscillations can be tuned for a fixed carrier density from 15 to 120 MHz by simply changing the applied bias. The frequency distribution within a certain voltage range can be varied by changing the density of photoexcited carriers. For larger carrier densities, higher frequencies are observed in a different voltage range. This system could therefore be used as a high-frequency oscillator, which can be controlled by two external parameters, the applied voltage and the light intensity. (C) 1996 American Institute of Physics.