In Ga As ∕ Al As Sb ∕ In P strain compensated quantum cascade lasers

The authors demonstrate the feasibility of strain compensated InGaAs∕AlAsSb∕InP quantum cascade lasers (QCLs). Three QCL structures have been investigated, having identical design but with different indium fractions in InxGa1−xAs quantum wells: 0.53 (lattice matched reference device), 0.6, and 0.7. All lasers display similar operating characteristics at λ≈4.1μm with no degradation of performance for the strain compensated devices. This strain compensated system is of interest for QCLs at λ<∼3.5μm. It provides increased energy separation between the Γ and X conduction band minima in the quantum wells, thus decreasing carrier leakage from the upper laser levels by intervalley scattering.