Investigation of Coulomb scattering in terahertz quantum cascade lasers

Abstract

Based on rate equation simulation, the impact of ionized-impurity and electron–electron scatterings on the device characteristics of terahertz (THz) quantum cascade lasers (QCLs) is investigated. This study applies the discretized Fourier transform to speed up the calculation of electron–electron scattering term and improves the calculation time by three orders without impairing accuracy. In addition, a screening effect model, which is necessary for the Coulomb scattering rate calculation, is also carefully selected. An indirectly pumped THz QCL and two types of direct resonant-phonon devices are chosen as examples in this study. The simulation results show that the influence of Coulomb scatterings varies according to device structures. Therefore, it is preferable to include physical models of these carrier scattering phenomena in the simulation when the highest operation temperature is predicted. In addition, this study also discusses the necessity of a pure dephasing time model.