Fast charge collection in GaAs MESFETs

Time-resolved charge collection measurements on 1- mu m-gate-length digital GaAs metal-semiconductor field effect transistors (MESFETs) with a variety of energetic ions and picosecond laser pulses exhibit risetimes as short as 25 ps with pulse widths of approximately 35 ps. Evidence is presented for the presence of three distinct-timescale charge collection processes, with time constants ranging from less than 25 ps to >1 mu s. The effects of radiation damage on the charge collection transients are presented, and the use of above-bandgap picosecond laser excitation is demonstrated as a viable alternative to ion excitation for characterization of the dynamical response of high-frequency, radiation-sensitive devices to rapid charge deposition. >