Non equilibrium electrons and phonons in quantum-cascade lasers
نویسندگان
چکیده
The electron-phonon interaction is the dominant process that controls the energy relaxation of carriers, in semiconductors and related heterostructures. If the excess energy of the electron ensemble is sufficiently high, the process of electron cooling may generate significant nonequilibrium electron and optical-phonon populations which may cause substantial changes in the carrier relaxation kinetics. These effects are expected to be pronounced in quantum cascade lasers (QCLs) which exploit the electron-phonon interaction to achieve population inversion between different conduction subbands. We will discuss the following results obtained using a combination of microprobe photoluminescence and Raman Stokes/AntiStokes spectroscopies: a) The non-equilibrium phonon population in InGaAs/AlInAs//InP mid-IR QCLs [1] and GaAs/AlGaAs THz QCLs based on the resonant-phonon active region scheme [2]. b) The electronic spatial distribution in In0.53Ga0.47As/AlAs0.56Sb0.44 mid-IR QCLs [3] and the electron-lattice relaxation in In0.53Ga0.47As/Al0.62Ga0.38As0.55Sb0.45 quaternary barrier mid-IR QCLs [4].
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