The energy level of the EL2 defect in GaAs

The free electron concentration in semi-insulating GaAs material is larger than the intrinsic concentration. This is due to the contribution of electrons originating from EL2 defects. The magnitude of this contribution implies that the energy level associated with this defect lies near 0.6 eV and not at 0.75 eV, as commonly assumed. We examine the various values which have been determined for this energy level and underline the difference found between photoluminescence and electrical techniques. We finally use a technique derived from deep level transient spectroscopy to get a direct measurement of this energy level. We obtain a value of 0.58 eV, which is consistent with all observations. (C) 1998 Elsevier Science Ltd. All rights reserved.