A Monte Carlo model of parallel high-field transport in III-V heterostructures is presented. Special features of the model are the following: only two-dimensional electron states are considered, the possible existence of secondary wells inside the barriers is accounted for, and nonparabolicity effect and quantization of satellite valleys are included. The wave functions and eigenenergies are calculated by self-consistent resolution of Poisson and Schrödinger equations. The effect of nonparabolicity on dispersion relations is determined at first order by a perturbation method. First, the simple case of an infinite GaAs square well is investigated as a test for the model, then more realistic heterostructures are considered. A study of a modulation-doped pseudomorphic AlxGa1−xAs/In0.15Ga0.85As structure shows that the electric field induces a significant repopulation of the doped AlGaAs layer. When x=0.32, this real-space transfer is strongly correlated with the intervalley transitions toward X valley states. For In0.52Al0.48As/In0.53Ga0.47As the situation is quite different and a good confinement in the InGaAs well is preserved even at high fields owing to the large band offset in the L valley. This study demonstrates a complicated influence of band structure on electron transport in heterostructures.
Articles you may be interested inResonant tunneling field-effect transistor based on wave function shape modulation in quantum wires Impurity scattering limited mobility in a quantum well heterojunction J.A theoretical investigation of impurity scattering limited mobility in a quantum wire is presented. The general method of mobility calculation is presented and some approximations are made in order to simplify the.problem and reduce the amount of computations. Cylindrical symmetry of the wire is assumed and the carriers are assumed to be confined by an in&rite barrier. The mobility has been computed using the exact wave functions and the results are compared with those obtained using constant or Dirac wave-function approximations. It is shown that the mobility is strongly influenced by the shape of the wave function. The screening effect is introduced using two different models. At high temperatures both models yield similar results whereas at low temperature a significant discrepancy is observed. The influence of important parameters such as wire dimension, carrier density, and temperature on impurity scattering mobility is investigated. A comparison of impurity scattering mobility in quantum well and quantum wire is also presented. Finally, it is shown that the electron-transport properties in quantum wires may be strongly enhanced by the use of a large spacer.
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