High field transport in semi-insulating GaAs: A promising material for solid-state detectors

Semi-insulating GaAs detector structures have been studied by transport [current–voltage (I–V) curves] and scanning electron microscope voltage (potential) contrast methods. The saturated part of I–V curves, suitable for radiation detection, is due to the velocity controlled high field transport mechanism while the sharp increase of current with voltage is ascribed to the impact ionization. It is shown that a modified voltage contrast method is able to reveal the actual potential distribution and to contribute to the optimization of the radiation detector structures.