Monte Carlo Simulations of THz Quantum-Cascade Lasers

This work is a theoretical study, compared with experimental data, on GaAs/Al0.15Ga0.85 As quantum-cascade laser structure operating at λ = 66 μm. The Monte Carlo method is used to give useful information about the electron dynamics in such structures, by extracting the electron population and distribution function at every step of the simulation. Electron wavefunctions and energies are calculated using a self-consistent non-parabolic Schrödinger-Poisson solver. Longitudinal Optical phonon, acoustic phonon and electron-electron scatterings are included. Finally non-equilibrium phonons have been explicitely considered and the Pauli's exclusion principle is taken into account. In addition, electroluminescence spectra and transition rates are calculated. Results show that population inversion occurs for an electric field F = 3.15 KV/cm at a temperature of T = 80 K. The electrons involved in the lasing action come from two different levels very close in energy. The electronic temperatures extracted from the distribution functions agree very well to the measured ones. The rates extracted during the simulation allow us to give a complete insight on the mechanisms responsible for the population and depletion of the laser levels.