Abstract

We have developed a fully quantum mechanical and self-consistent non-equilibrium Green's function (NEGF) theory for quantum cascade lasers (QCL). This method takes into account acoustic, polar-optical phonon scattering, impurity, and interface roughness scattering within the self-consistent Born approximation. We present detailed results for the carrier transport and optical gain in a regime where multiple scattering, interference effects, carrier confinement and capture play an equally important role. The previously neglected [1] momentum and energy dependence of the scattering mechanisms is shown to have a significant influence on all QCL device characteristics. The electron-electron scattering is incorporated self-consistently within the Hartree approximation. The coupling between the lesser and the retarded Green's function is fully taken into account. In this way, all scattering states, transition probabilities, and occupancies are calculated self-consistently with one another which avoids artifacts such as the violation of Pauli blocking that has plagued previous schemes.

© 2007 IEEE