High-speed Al/sub 0.2/Ga/sub 0.8/As/GaAs multi-quantum-well phototransistors with tunable spectral response

The authors have measured the high-frequency characteristics and temporal response of a GaAs/AlGaAs heterojunction phototransistor with a GaAs/Al/sub 0.2/Ga/sub 0.8 /multi-quantum-well collector. The quantum wells offer tunability of the photoresponse (10 nm for a bias change of 4 V) and a negative differential resistance in the photocurrent-voltage characteristics. Measured values of f/sub T/ and f/sub max/ are 20 and 6 GHz, respectively. The temporal response to short-pulse optical excitation is characterized by a linewidth of 46 ps. Such devices are attractive candidates for making optically induced oscillators.<
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