Intraband transitions in quantum dot–superlattice heterostructures

We present a scheme of adjusting the mid-infrared absorption properties to desired energy transitions in quantum dot-based photodetectors by combining band gap engineering with the self-organized growth of quantum dots. Embedding the self-organized InAs quantum dots into an AlAs∕GaAs superlattice enables us to tune the optical transition energy by changing the superlattice period as well as by changing the growth conditions of the dots. Using a one-band envelope function framework, we are able, in a three-dimensional calculation, to predict the absorption spectra of these devices as well as their polarization properties. These calculations further predict a strong impact of the dots on the superlattice minibands. By comparing aligned, periodic dot stacks with nonperiodic dot arrangements within the superlattice, we can experimentally confirm this prediction.