Space charge formation in chromium-compensated GaAs sensors is investigated by the laser-induced transient current technique applying pulsed and DC bias. Formation of non-standard space charge manifested by an appearance of both negatively and positively charged regions in DC biased sensors was revealed during 5 ms after switching bias. Using Monte Carlo simulations of current transients we determined enhanced electron lifetime {tau} = 150 ns and electron drift mobility {mu}d = 3650 cm2/Vs. We developed and successfully applied theoretical model based on fast hole trapping in the system with spatially variable hole conductivity.
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