| The study of high field transport has been instrumental to the theory of many semiconductor devices based on, e.g., the Hilsum-Ridley-Watkins mechanism, impact ionization phenomena, and recently real space transfer. It will become even more important as device sizes approach submicron dimensions. Current interest in small devices concerns not only scaling down and VLSI (very large scale integration) but also phenomena such as size quantization, real space transfer, and velocity overshoot, which was recently termed ballistic transport.;The speed enhancement of injecting electrons over the Al(,x)Ga(,1-x)As-GaAs hetero-barrier is studied. The results show that a narrow "collision free window" exists with respect to parameters such as the electric field, the injection energy, the external voltage, and the semiconductor dimension. It is found that only emitter(source)- and base-like structures are eligible for collision-free transport; collectors(drains) are not because of unavoidable high voltage drops.;The emission of hot electrons from the silicon substrate to the silicon dioxide is studied. By a detailed investigation of the steady state transport phenomena in silicon, three sets of transport parameters are found. A Monte Carlo simulation which includes two realistic conduction bands and the spatial variation of the electric field is then performed to study the high energy tail of the distribution fuction.;Recently, the validity of the semiclassical Boltzmann transport equation has been reexamined and quantum corrections for the transport equation have been suggested. The quantum aspects of the transport problem are discussed. A quantum Monte Carlo method is proposed and various quantum effects are examined. The study indicates that the most important quantum correction is the self-energy effect which amounts to a quasi-particle Boltzmann transport equation. The intra-collisional field effect is shown not to be important in a steady state situation.;A Monte Carlo simulation, including a pseudopotential band structure, is chosen for this study. It is shown in this study that this method can be applied to both the steady state and the transient state transport problems. |
