Strongly anisotropic field ionization of a common deep level in GaAs

Abstract

We observe a very strong anisotropy of the internal field effect for defect « EL2 » (a well-known deep level, assigned in the past to oxygen) in GaAs. The ionization rate is maximum when the electric field is 111 oriented, pointing from As, to Ga and is minimum for the opposite 111 field orientation. Conclusions concerning the microscopic defect structure can be deduced from this behaviour. This new method of investigation of the symmetry properties of deep level defects can be more generally applied to all the levels emitting into the conduction band of GaAs, its related compounds and any other high-mobility semiconductor