A study on the photoconductivity of a set of horizontal Bridgman semi-insulating GaAs ingots

The authors report in this paper a study of the photoconductivity of a set of Horizontal Bridgman semi-insulating GaAs samples. In order to obtain steady-state photoconductivity spectra, they measure the photocurrent by a procedure that consists in thermally erasing the typical GaAs photomemory. The thermal evolution, between 80 and 300 K, of the photoconductivity is also obtained. The data so obtained allow us to distinguish clearly a diversity of behaviors between the photoelectronic properties of the different samples, which could not be observed with the conventional photoconductivity technique. The way in which chromium and oxygen impurities are introduced in GaAs, as well as their charge states, seem to be strongly influenced by native defects and background impurities, which play an important role in the compensation mechanism.