Terahertz quantum cascade laser considering compositional interdiffusion effect

Abstract

This study presents an experimental demonstration of the crucial role of compositional interdiffusion at interfaces in GaAs/AlGaAs alternating superlattices for developing the terahertz quantum cascade lasers operating at high temperatures. By growing GaAs/Al0.3Ga0.7As superlattices using the molecular beam epitaxy technique, an aluminum interdiffusion width of 0.95 nm (equivalent to ∼3.4 monolayers) is estimated. Incorporating this interdiffusion width as an additional design parameter has resulted in a 20 K improvement in the maximum operating temperature of the laser. To quantify the magnitude of the interdiffusion scattering effects on electron dynamics, an independent self-energy that functions based on the axial correlation length is introduced in the non-equilibrium Green’s function model. It clarifies that changes in the lifetime of quantum states and also the population fractions are primarily influenced by the deformation of wave functions at the injector when the interfaces become interdiffused.