IR quantum dot detectors with miniband tunnel extraction

By combining band gap engineering with the self-organised growth of quantum dots we present a scheme of adjusting the mid-infrared absorption properties to desired energy transitions in quantum dot based photodetectors (QDIPs). Embedding of the self organised 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. In addition the dark current is significantly reduced by more than one order of magnitude compared to QDIPs without a superlattice. Furthermore, the impact of vertical dot alignment on the tunnelling properties of the photoexcited electrons is investigated.