Fast charge collection in GaAs MESFETs

Time-resolved charge collection measurements on 1-μm-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 ~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 μs. 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