OPTICAL TRANSIENT CURRENT SPECTROSCOPY FOR TRAPPING LEVELS IN SEMIINSULATING LEC GALLIUM-ARSENIDE

Optical transient current spectroscopy (OTCS) is a member of the class of deep level transient spectroscopy (DLTS) techniques. Its advantange is that, unlike other DLTS techniques, it can be applied o semi-insulating GaAs (which is the starting material for integrated circuit (IC) fabrication). The aim is to obtain information on deep trapping levels, which may be fundamental interest and is certainly of practical interest since it can help in diagnosing the suitability of the material for IC fabrication. We have investigated the method using different device geometries, electrode materials, surface preparations, and GaAs crystals. Various 'peaks' in the OTCS spectrum were identified, including EL2, the center responsible for the semi-insulating property in undoped LEC GaAs.