ABSTRACT
Quantum Well Infrared Detectors operate on account of intersubband transitions in doped quantum wells (QWs) which implies photoexcitation of charge carriers from a bound ground state to quasi-bound or extended excited states where the charge carriers are freely mobile perpendicularly to the QW planes, thus enabling photoconductive action. The absorptance for normally incident radiation can be enhanced and become polarisation independent by the use of a crossed grating with a cladding layer and reach values close to unity for large detector mesa sizes. In order to theoretically model the absorptance properties of a QW infrared detector it is necessary to find proper models of its main constituents, i.e., the grating and the QW structure. The anisotropic properties of infrared absorption in the QW structure are modeled by a transfer matrix method, which also takes multiple internal reflection between layers into account.
