Experimental investigation of terahertz quantum cascade laser with variable barrier heights

We report an experimental study of terahertz quantum cascade lasers with variable barrier heights based on the Al_xGa_1–xAs/GaAs material system. Two new designs are developed based on semiclassical ensemble Monte Carlo simulations using state-of-the-art Al_0.15Ga_0.85As/GaAs three-quantum-well resonant phonon depopulation active region design as a reference. The new designs achieved maximum lasing temperatures of 188 K and 172 K, as compared to the maximum lasing temperature of 191 K for the reference structure. These results demonstrate that terahertz quantum cascade laser designs with variable barrier heights provide a viable alternative to the traditional active region designs with fixed barrier composition. Additional design space offered by using variable barriers may lead to future improvements in the terahertz quantum cascade laser performance.