The effects of various approximations on electron-electron scattering calculations in QCLs

Quantum cascade lasers (QCLs) employ the midand far-infrared intersubband radiative transitions available in semiconducting heterostructures. Through the precise design and construction of these heterostructures the laser characteristics and output frequencies can be controlled. When fabricated, QCLs offer a lightweight and portable alternative to traditional laser systems which emit in this frequency range. The successful operation of these devices strongly depends on the effects of electron transport. Electron-electron scattering is an essential mechanism involved in electron transport and approximations are often made in finding the electron-electron scattering rate in order to simplify calculations. Results will be presented characterizing various effects which are sometimes ignored in calculating electron-electron scattering rates. These effects include state-blocking, electron screening, temperature dependence, as well as the inclusion of all possible transitions that can occur in three periods of the QCL active region. These effects will be presented in the context of several QCL active region designs, including those grown and fabricated at the University of Massachusetts Lowell Photonics Center.