Interface Phonon Modes in Quantum Cascade Lasers

We investigate the interface phonon assisted transition in GaAs/AlGaAs quantum cascade lasers (QCLs) by using the transfer matrix method based on the dielectric continuum model. Electron eigenvalues and eigenstates are calculated by solving Schrödinger equation and the Poisson equation self-consistently. The AlAs-like and upper GaAs-like interface phonon modes contribute most of the scattering rate. Interface phonon modes couple strongly with electrons at E₂, and the magnitude of scattering rate between E₂ and E₁ is much larger than that between E₃ and E₁, which is helpful for the laser inversion between E₃ and E₂. The calculation can be easily applied to the design and simulation of QCLs.