Voltage-tunable two-color quantum-dot infrared photodetectors

A two-terminal quantum-dot infrared photodetector with stacked five-period InAs/GaAs and InGaAs-capped InAs/GaAs quantum-dot (QD) structures is investigated. The device has exhibited distinct responses at mid-wavelength and long-wavelength infrared regions under positive and negative biases, respectively. The results suggest that the QD confinement states near the anode side are completely filled, such that selective responses at different wavelength ranges would be observed for the stacked structure under different voltage polarities. Also observed are the similar absorption ratios of the device under different incident light polarizations at the two response regions.