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A three-terminal a-Si/Si(p)/Si(n) heterojunction device was found to generate pulses of the collector current with a rise time of approximately 10 −7 s and a fall time of approximately 4 × 10 −7 s. The voltage applied to the base (0.8-1.5 V) controlled the pulse repetition rate. When the voltage reaches ∼1.0 V, the pulses start to overlap, and the output signal is a high-frequency oscillation (10 6 -10 7 Hz) of the collector current.A simple mechanism explaining the pulse generation and the high-frequency oscillations has been proposed. It involves the extremely high recombination rate of the injected carriers in the thin a-Si layer of the a-Si/Si(p) interface.

The electrical I -U characteristics of the three-terminal device a-Si/Si(p)/Si(n) have been investigated. The device shows both transistor and switching behaviour depending on the magnitude of the base current. The influence of the base current on the holding and switching voltages has been studied.A model describing this behaviour of the device has been suggested. It is based on the existence of a narrow region adjacent to the a-Si/Si(p) junction, characterized by an extremely high recombination rate of the injected carriers.

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