Effect of Schottky barrier height on EL2 measurement by deep-level transient spectroscopy

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Abstract
A systematic study of EL2 midgap trap in GaAs using deep-level transient spectroscopy (DLTS) is reported for contacts having a large range of Schottky barrier height. The results show that the DLTS signal of EL2 increases as the barrier height rises from 0.62 eV and saturates for barrier height above 0.83 eV. It is found, for the first time, that for Schottky barrier height lower than 0.62 eV the EL2 signal disappears. A model for calculation of the quasi-Fermi level in the depletion region is used to explain the variation and disappearance of the EL2 signal. This model may also apply to other electron traps near midgap.