Analysis of time-dependent current transport in an optically controlled Cu-compensated GaAs switch

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Abstract
The bulk optically controlled semiconductor switch (BOSS) is a concept based on modulating the bulk conductivity (sigma) of copper-compensated, silicon-doped gallium arsenide (GaAs:Si:Cu). Using laser light at (lambda) equals 1 micrometers , (sigma) can be increased to greater than 1 ((Omega) cm)-1, and then returned to values comparable to the equilibrium value of (sigma) < 10-4 ((Omega) cm)-1 by illuminating the bulk with an infrared laser at (lambda) approximately equals 2 micrometers . This reversible process forms the switching cycle of the BOSS device. Experimental verification of the essential features of the BOSS switching cycle has been reported at low values of current density; however, power scaling experiments have revealed behavior too complex to be explained by a zero-dimensional model based strictly on conductivity. For this reason, a one- dimensional time-dependent computer code has been developed to analyze the effects of current transport and spatial inhomogeneity in a BOSS device. Electron and hole transport are modeled self-consistently with electron and hole continuity equations and the Poisson equation. The computer code includes the effects of deep-level trapping kinetics, and the boundary conditions model those of a forward-biased p-i-n device. The low-current density results of the 1-d model are verified against the 0-d conductivity model; deviations from the 0-d model as the current density is increased are reported and qualitatively compared against available power-scaling data.

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