TEMPORAL DEVELOPMENT OF ELECTRIC-FIELD STRUCTURES IN PHOTOCONDUCTIVE GAAS SWITCHES

The temporal development of the electric field distribution in semi-in sulating GaAs photoconductive switches operated in the linear and lock -on mode has been studied. The field structure was obtained by recordi ng a change in the absorption pattern of the switch due to the Franz-K eldysh effect at a wavelength near the band edge of GaAs. In the linea r mode, a high field layer develops at the cathode contact after laser activation. With increasing applied voltage, domainlike structures be come visible in the anode region and the switch transits into the lock -on state, a permanent filamentary electrical discharge. Calibration m easurements show the field intensity in these domains to exceed 40 kV/ cm, which is greater than three times the value of the average applied field.