Intervalley scattering in terahertz quantum cascade lasers with GaSb and InGaSb wells

We theoretically study the performance of terahertz quantum cascade lasers (THz-QCLs) with GaSb wells and InxGa1−xSb wells. The results of rate-equation calculations reveal that the intervalley scattering of electrons from the Γ valley to the L valley in GaSb degrades the performance of the GaSb-based THz-QCLs at high temperatures. We propose the use of InxGa1−xSb (x ≥ 0.25) quantum wells to reduce the intervalley scattering. Our calculations using the nonequilibrium Green’s function method including alloy disorder scattering show that the THz-QCLs with InGaSb wells have higher gain than the GaAs-based THz-QCLs at high temperatures.