Abstract

Unmodified InAlAs/InGaAs heterojunction bipolar transistors were illuminated with visible-wavelength femtosecond pulses; electrical responses were measured electro-optically. 2.4-ps emitter photocurrent transients, corresponding to a bandwidth in excess of 200 GHz, were observed. Slow photocurrent components due to holes trapped in the base could be eliminated with appropriate base biasing. An equivalent-circuit model successfully accounts for the observed photocurrents.

© 1993 Optical Society of America