Dual Band Normal Incidence Quantum Well Intersubband Photodetector

GaAs-based Quantum Well Intersubband Photodetectors (QWIP's) are very attractive devices for large staring Focal Plane Arrays) FPA's) at mid and long infrared wavelengths. The mature GaAs processing technology allows larger arrays with higher pixel operability and better uniformity to be manufactured at lower cost than competing technologies that can access both the MWIR (3-5 micron) and LWIR (8-12 micron) atmospheric windows. Detection in both wavelength ranges with a single array is also easily obtainable with vertical integration. This proposal aims to develop an improved two color QWIP which can image at normal incidence without the need for a diffractive coupler. In addition to reducing processing complexity and improving pixel to pixel uniformity, this approach has the potential to reduce the dark current in the FDIR detector by enabling the barriers between the wells to be composed of a direct bandgap material rather than an indirect one.