Slow domains in semi-insulating GaAs

Semi-insulating GaAs shows current oscillations if a high dc voltage is app lied to a sample. These oscillations are caused by traveling high-electric- field domains that are formed as a result of electric-field-enhanced electr on trapping. This article describes the various types of experiments that h ave been carried out with this system, including recent ones that use the e lectro-optic Pockels effect in order to measure the local electric fields i n the sample in a highly accurate manner. An historical overview of the the oretical developments is given and shows that no satisfying theory is curre ntly available. A list of all the required ingredients for a successful the ory is provided and the experimental data are explained in a qualitative ma nner. Furthermore, the main electron trap in semi-insulating GaAs is the na tive defect EL2, the main properties of which are described. (C) 2001 Ameri can Institute of Physics.