Investigation of detection wavelength in quantum dot infrared photodetector

Abstract

A quantum dot infrared photodetector (QDIP) consisting of highly Si-doped self-assembled In0.5Ga0.5As quantum dots (QDs) has been studied. High Si-doping in the QDs has been introduced to provide large carriers for infrared (IR) absorption and an Al0.3Ga0.7As blocking layer has been inserted for reducing dark currents. Spectral responses of QDIP have been obtained for vertical incident IR. light on a detector from 4 mum to 8 mum with biases ranging from -260 to 260 meV at 10 K. Large dark currents have been measured at 80 K, prohibiting detection of spectral response, even though an AlGaAs blocking layer was introduced. The large dark currents may be due to high doping density in the QD structure. The broad spectral response in a narrow bias voltage range is thought to be due to the high doping in QDs which may fill all confinement states of the conduction band in QDs.