Interface roughness/island effects on intersubband transitions in quantum wells

Abstract

We introduce a perturbation approach to study interface roughness/island electron diffraction effects in quantum wells and apply this approach to photoexcitation and infrared detection. Interfacial imperfections spoil the usual selection rules associated with intersubband optical transitions, thereby making transitions due to photons polarized in the plane of the quantum well non-forbidden. This can have a beneficial effect since normal incidence photoexcitation would provide the simplest approach to detector, modulator, and focal plane array applications. A general result for quantum well interfaces with arbitrary (random or regular) island patterns is obtained. Some estimates of the effect are included. In addition, the effect of interface roughness on intrasubband transitions is briefly discussed.