Improved hold-off characteristics of gallium arsenide photoconductive switches used in high power applications

Electron injection and the subsequent formation of a trap filled region leads to premature device failure in an opposed contact, EL2/carbon compensated GaAs photoconductive switch, made through the liquid encapsulated Czochralski process. Due to the electrostatic properties associated with an n/sup +//semi-insulating junction, the introduction of an n/sup +/ region next to the cathode suppresses electron injection until higher bias. The doping level, length, and the thickness of the high n/sup +/ region are some of the parameters that affect hold-off characteristics. Extending the length of the n/sup +/ region well beyond the cathode does not increase the hold-off voltage but confines current flow to a narrow strip, which may trigger local heating burnout. Suppression of the effects of the EL2 traps at the n/sup +//SI interface also does not improve the hold-off characteristics. Opposed contact switches, made from intrinsic GaAs have the characteristics of ´relaxation´ semiconductors. The injection of minority carrier results in initial recombination and the formation of a large number of recombination regions may contribute to switching delays and jitters.