THEORETICAL STUDIES OF HIGH ENERGY TRANSPORT OF ELECTRONS AND HOLES IN GALLIUM-ARSENIDE, INDIUM-PHOSPHIDE, INDIUM-ARSENIDE, AND GALLIUM-ANTIMONIDE (SEMICONDUCTORS, MONTE CARLO, IMPACT IONIZATION)

In this thesis, the high field behavior of both electrons and holes is studied using a Monte Carlo calculation including a complete band structure. The Monte Carlo method is particularly useful since it can be applied to both steady state and transient problems.;The impact ionization rate of both electrons and holes is calculated including quantum effects. It is found that the electron impact ionization rate is larger in GaAs than in InP because of the higher ionization threshold energy and greater density of states in InP. The electron ionization rate is greater than the hole ionization rate in GaAs because the electrons can drift to energies at or above the threshold energy, which is the same for both carriers, easier than the holes can. In InP, the hole ionization rate is larger than the electron ionization rate because the hole threshold energy is smaller than the electron ionization threshold energy.;Among the transient transport problems examined is velocity overshoot of both electrons and holes in GaAs, InP and InAs. It is determined that there exists a narrow range of parameters such as the applied electric field, the initial condition (launching energy and momentum), the boundary condition at the collecting contact, and the semiconductor dimensions that result in significant velocity overshoot. The calculations show that the overshoot is greater in InP than in GaAs. This is because the valley separation energies are larger in InP so the electrons are more easily confined to the low effective mass gamma valley.;Extended velocity overshoot is attainable through use of staircase heterostructures. The excess kinetic energy gained by the electrons from an overlaid applied electric field is lost by making the electrons 'climb' a series of potential steps. In this way the electrons are confined to the gamma valley where they can achieve high drift velocities.;The calculated steady state high field properties include the drift velocity and the impact ionization rate. It is determined theoretically that in either GaAs or InP the electron and hole steady state drift velocities are roughly the same. The calculated carrier drift velocities in InP are larger than in GaAs.