Identification of oxygen-related midgap level in GaAs

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Abstract
An oxygen-related deep level ELO was identified in GaAs employing Bridgman-grown crystals with controlled oxygen doping. The activation energy (825±5 meV) of ELO is almost the same as that of the dominant midgap level: EL2 (815±2 meV). This fact impedes the identification of ELO by standard deep level transient spectroscopy. However, we found that the electron capture cross section of ELO is about four times greater than that of EL2. This characteristic served as the basis for the separation and quantitative investigation of ELO employing detailed capacitance transient measurements in conjunction with reference measurements on crystals grown without oxygen doping and containing only EL2.