Defect Heterojunction Model for Anomalous Photoresponse of P/N GaAs Grown on N-Ge Substrates

Abstract

ABSTRACTA GaAs p/n junction grown on a n-Ge substrate has an anomalous photoresponse that includes a quantum yield response starting at the 0.7-eV band edge of Ge. In terrestrial sunlight, its I-V characteristic has an anomalous “notched” shape that is progressively removed by increasing the infrared light content. The I-V is well modeled by a space-charge-limited-current diode theory with a GaAs/Ge interface defect density of 1.92 (1012) cm−2 eV−1 at 0.4 eV below the conduction band edge. Similar defect densities have been reported for GaAs/oxide interfaces and for a GaAs p/n junction interface specially selected for high defect densities.