Abstract
Separation of the electron and hole traps in semi-insulating GaAs by changing the polarity of bias voltage in the thermally stimulated current measurement is done more distinctly when the photo excitation for initialization is confined to the thinned region of the improved specimen, rather than illumination over the whole front surface as previously reported. It was found that this rambling component of the transient current was suppressed by applying an electric field in the order of 103 V/cm.