INFRARED PHOTOCONDUCTIVITY VIA DEEP COPPER ACCEPTORS IN SILICON-DOPED, COPPER-COMPENSATED GALLIUM-ARSENIDE PHOTOCONDUCTIVE SWITCHES

Silicon-doped, copper-compensated, semi-insulating gallium arsenide of various doping parameters has been studied with respect to infrared p hotoconductivity. This material is used as a photoconductive switch kn own as the Bistable Optically controlled Semiconductor Switch (BOSS). This device is a candidate for use in high-power, frequency agile puls ed power applications. One limitation has been the relatively low cond uctivity of the device during the ''on-state.'' Typically, silicon-dop ed gallium arsenide is converted to semi-insulating gallium arsenide b y the thermal diffusion of copper into the GaAs:Si. We have shown that variation of the diffusion parameters can improve the on-state conduc tivity by the enhancement of the concentration of a copper center know n as CUB. The conductivity of the device 150 ns after irradiation from a 20-ns FWHM laser pulse (lambda = 1.1 mum) is recorded for various i ncident energies. This on-state conductivity saturates at a value that is predicted by the densities of the copper levels and the mobility. Also, the samples were irradiated with a 140-ps FWHM laser pulse (lamb da = 2 mum) in order to excite holes from the copper levels into the v alence band which demonstrates the nature of the hole recapture into t he various copper acceptors.