Effects of a drift in GaAs growth rate on the electronic transport in resonant phonon terahertz quantum cascade lasers

On the basis of a proven design (Liu 2005 et al Appl. Phys. Lett. 87 141102), terahertz quantum cascade laser structures are obtained by altering the GaAs component growth rate to the range of +/-10%. The influences of the growth rate on electronic transport and electric output are investigated by an ensemble Monte Carlo simulation, including electron-electron and electron-LO phonon scattering. Calculations indicate two important channels for leakage current. One is from upper radiative states to extract states and the other one is from injection states to lower radiative states. With the increase of the GaAs growth rate, the leakage current from the first channel is reduced greatly, resulting in the enhancement of population inversion and the decrease of the current density. The dependence of electric field-current density characteristics on the GaAs growth rate is in agreement with recent experimental measurement.