Transport and carrier dynamics in high-resistivity semiconductors

This dissertation presents investigations of charge transport in high-resistivity semiconductors, an area which has received little attention compared to most commercial semiconducting materials. Understanding the behavior of carriers injected into semiconductors is essential to the continuing development of electronic and opto-electronic devices. The system of interest in this study is high-purity silicon at cryogenic temperatures which has a high resistivity due to the low carrier concentrations in the material. Although this work focuses on non-equilibrium carrier behavior in silicon, the related physics in applicable to any large band-gap/low trap density material which may find use in the future.;The experiments characterize charge-dominated (relaxation regime) transport which occurs when the dielectric relaxation time ;A numerical analysis is performed to provide a valid representation of the specific problem which involves strongly coupled Poisson's equation and continuity equations. The modelling results indicate that, at cryogenic temperatures (approximately 20 K), where the relaxation time is comparable to the lifetime, space-charge dominated transport occurs and charge storage which manifests itself in the form of an additional capacitance.;A.C. measurements are made on high-purity silicon at various temperatures ranging from 300 K to 11 K. Capacitance profiles are calculated from the a.c. data and presented as a function of temperature to verify for the first time the existence of a space-charge dipole which is formed due to carrier transport in the relaxation regime. D.C. data illustrate the linear low-bias I-V characteristics which result from space-charge transport. This work also compares results performed in dark and black-body illuminated conditions to verify the physics of relaxation regime transport. In all, these studies present unique transport properties in a high-purity semiconductor where space-charge dominated transport is responsible for dipole formation and linear I-V characteristics.