Simulation of quantum cascade lasers using Robin boundary conditions

We present a study on tunneling current density and an investigation of the optical gain of GaAs/Al
_x
Ga
_1-x
As quantum cascade lasers. Current carrying states are obtained by taking into account Robin boundary conditions. Our simulation results show that this approach gives a very good agreement with other calculations using the Tsu-Esaki model and with simulations based on nonequilibrium Green's functions. Furthermore, by incorporating this method into optical gain calculations we establish good agreement with experimental results.