HIGH-VOLTAGE PICOSECOND PHOTOCONDUCTOR SWITCH BASED ON LOW-TEMPERATURE-GROWN GAAS

A GaAs material grown by molecular beam epitaxy (MBE at a low substrate temperature was used to fabricate a photoconductor switch that produces 6-V picosecond electrical pulses. This is the highest impulse voltage with a picosecond duration ever generated. The low-temperature (LT) GaAs is well suited for application to high-volt-age picosecond switching, because it has a high dark resistivity, a high dielectric-breakdown strength, a subpicosecond carrier lifetime, and a high minority-carrier mobility. The pulses were produced on a microwave coplanar-strip transmission line lithographically patterned on the LT GaAs. A 150-fs laser pulse was used to generate carriers in the LT GaAs gap between the metal strips, partially shorting a high dc voltage placed across the lines. The 6-V magnitude of the electrical pulses obtained is believed to be limited by the laser pulse power and not by the properties of the LT GaAs. Experiments were also performed on a picosecond photoconductor switch fabricated on a conventional ion-damaged silicon-on-sapphire substrate. Although comparable pulse durations were obtained, the highest pulse voltage achieved with the latter device was 0.6 V. © 1990 IEEE