| Electron transport in III-V semiconductors, especially the GaAs/AlGaAs material system, is studied in various nonequilibrium situations. Throughout the study, a Monte Carlo simulation method is used for the analysis of transport properties in the semiclassical Boltzmann transport picture. The present work essentially consists of two aspects. The first topic is hot electron transport in GaAs, focusing on the electron impact ionization effects. The dependence of impact ionization rates on the details of the band structure is investigated by using two (local and non-local) pseudopotential methods. The spatial evolution of the ionization rate and the average electron energy are studied in nonuniform fields characteristic of p;The second aspect deals with the effects of conduction band discontinuities on the electron transport. In particular, one-dimensional heterostructures are modeled to study the nonlinear transport across heterointerfaces. First, two heterostructure avalanche photodiodes are studied. It is found that overheating, enhanced energy relaxation, and carrier confinement as a consequence of the structure in real space have a pronouned influence on the energy and momentum distribution. As a result, the energy distribution can directly reveal the band structure of the material. The dependence of the impact ionization rate on the band structures of the neighboring layers is also addressed.;The effects of a nonequilibrium phonon distribution on the electron transport are studied as well. The phonon distribution can be considerably perturbed when a large number of carriers propagate across an interface, experience an abrupt energy gain, and subsequently relax through strong phonon emission. An algorithm is developed for the microscopic analysis of phonon dynamics. It is observed that the hot phonons change the scattering rate significantly, and heat the electron energy distribution.;To investigate quasiballistic electron motion, tunneling hot electron transfer amplifier structures are studied at 4.2 K. The numerical results demonstrate the existence of nearly ballistic transport in the base and in the collector barrier, and confirm that the experiments can indeed measure the energy distribution of injected ballistic electrons. The device characteristics, such as transfer ratio and transit time, are also investigated in detail. |
