Longitudinal Magnetophonon Resonances in Semiconductor Superlattices

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The presence of a quantizing magnetic field strongly modifies the electronic properties of semiconductor superlattices (SLs). When a strong magnetic field is applied normal to the heterointerfaces and parallel to the electric field (the longitudinal configuration), transport becomes quasi-one-dimensional (Q1D). Provided the Landau level miniband (LLMB) is well resolved, resonant scattering of longitudinal optical (LO) phonons gives rise to the magnetophonon resonance (MPR). We performed ensemble Monte Carlo simulations of the electron motion in a Landau-quantized GaAs/AlAs superlattice at high temperatures, taking account of various optical-phonon modes, to investigate effects of multi-mode behavior of optical-phonons. We find that a strong drift-velocity enhancement occurs under the cyclical phonon emission and absorption condition as predicted by Dalton et al.Electronic states and transport properties of a quasi-one-dimensional system in Landau-quantized superlattices are investigated using the nonequilibrium Green's function technique developed by Wacker and co-workers [A. Wacker, Phys. Rep., 357, 1 (2002)]. The quantum results are compared with the respective results obtained from Monte Carlo simulation of Boltzmann's transport equation. Our calculation focuses on the form of the velocity-electric-field curve in the region of increasing Wannier-Stark (WS) localization. We find that the current flow is strongly modulated by a subtle interplay of Stark cyclotron resonance (SCR) and optical phonon resonance (OPR).