Comparison between NEGF simulation and experimental results of Terahertz quantum cascade lasers

Nowadays quantum cascade lasers (QCLs) are the most promising candidates to enter the commercial market as semiconductor based sources for terahertz applications. However, the final breakthrough has not yet been achieved since operating temperatures of THz QCLs are still requiring cryogenic cooling. The record design reaches 178 K in pulsed mode, not accessible by thermoelectric coolers. In order to optimize the active region design even further, one needs a sophisticated transport theory including all relevant scattering mechanisms, resonant tunnelling and decoherence effects combined with realistic gain calculations. In collaboration with Prof. Vogl´s group from the Walter Schottky Institute we used a model based on non-equilibrium Green´s functions (NEGF) to redesign our active region.