Influence of the material parameters on quantum cascade devices

An experimental investigation on the influence of the material systems on the optical properties of quantum cascade structures is presented. Three electroluminescent quantum cascade devices have been grown using GaAs/AlGaAs, GaInAs/AlInAs, and InAs/AlSb heterostructures. The devices emit at 10 mu m and are based on a similar bandstructure design. Our results verify that the optical quantum efficiency has the predicted dependence on the electron effective mass. We also demonstrate that the shape of the electroluminescence spectra is independent from the particular material parameters and mainly depends on the tunnel coupling between the injector state and the upper state of the radiative transition. (C) 2008 American Institute of Physics.