A Theoretical Study On Mechanisms Of Nonequilibrium Carrier Relaxation In A GaInAs Alloy Quantum Well In A Strong Magnetic Field

In a few recent experiments, a magnetic field B applied parallel to the growthdirection of a quantum cascade laser (QCL) as an external parameter modulates thenon-radiative relaxation channels in the device, such as alloy disorder scattering andoptical phonon scattering, and results in a 1/B oscillation of the output. In the theoryof carrier relaxation in the alloy material quantum wells as units of the QCL, any com-putation using a regular Fermi's golden rule to estimate phonon scattering rates has toassume the electron-phonon interaction only results in perturbations to the alloy states.In the weak electron-phonon coupling regime, we use the Fermi's golden rule andhave a reasonable estimate of the acoustic phonon scattering from the alloy disorderedstates in a GaInAs well, while the result of fast scattering by optical phonons is ratherquestionable. Therefore,in the case of strong LO phonon scattering, a numerical di-agonalization computation is carried out. In the strong electron-LO phonon couplingregime, we use a magneto-polaron formalism and compute the electron upper levelsurvival probabilities, which also demonstrates rapid relaxation processes around a op-tical phonon scattering resonance magnetic field, where the alloy disorder in the wellplays a key role. With the interests in the magneto-polarons as high energy states in thenonequilibrium electron system, we take into accounts of an additional in-plane electricfield in a perfect material system to investigate the dissociation of the magneto-polaronstates. We compute a mid-infrared linear optical absorption by an ideal well, and pre-dict fine structures of intersubband absorption peaks related to the polaron states. Thedensity of states (DOS) of an alloy material in the crossed magnetic and electric fieldsare also computed, and structures at the DOS tails due to alloy scattering are found.