Low strain multiple stack quantum dot infrared photodetectors for multispectral and high resolution hyperspectral imaging

Quantum dot infrared photodetectors (QDIP) have received considerable interest for over a decade due to their sensitivity to normal incidence radiation and long excited carrier lifetimes. We report on a series of QDIPs with 30-80 GaAs-AlGaAs DWELL stacks. Dark current in these devices is constant at a given electric field, indicating that strain does not increase significantly as the number of DWELL stacks are increased. Each QDIP shows high responsivity and specific detectivity as well as a spectral response that varies significantly with applied bias. Four different spectra obtained at different applied biases on the 80 stack QDIP, with peak wavelengths ranging from 5.5mum to 10.0mum is shown. The wide variation in shape and peak wavelength of the intrinsic responses makes these QDIPs very attractive as multispectral imagers in the MWIR and LWIR regions.