Electron Transport Simulations and Band Structure Calculations of New Materials for Electronics: Silicon Carbide and Carbon Nanotubes

Title of dissertation: ELECTRON TRANSPORT SIMULATIONS AND BAND STRUCTURE CALCULATIONS OF NEW MATERIALS FOR ELECTRONICS: SILICON CARBIDE AND CARBON NANOTUBES. Gary Pennington, Doctor of Philosophy, 2003 Dissertation directed by: Professor Neil Goldsman Department of Electrical Engineering Silicon carbide (SiC) and carbon nanotubes (CNTs) are two materials which have promising potential in electronics. Due to its large bandgap and large thermal conductivity, SiC is targeted as a potential material for use in high-power hightemperature electronics. Carbon nanotubes are at the forefront of current research in nanoelectronics, and field-effect nanotube transistors have already been developed in research laboratories. The small dimensions of these materials suggests their possible use in densely packed CNT-integrated circuits. Carbon nanotubes also appear to have very large electron mobilities, and may have applications in highspeed electronic devices. In this work the properties of the electronic structure and electron transport in silicon carbide and in semiconducting zig-zag carbon nanotubes are studied. For SiC, a new method to calculate the bulk band structure is developed. The conduction band minimum is found to lie at the L and M points in the Brillouin zones of 4H and 6H-SiC respectively. The quasi-2D band structure of hexagonal SiC is also determined for a number of lattice orientations. Electron transport in SiC is investigated in the bulk and at the SiC/oxide interface. The dependence of transport on the lattice temperature, applied field, and crystal orientation is studied. A methodology for semiclassical transport of electrons in semiconducting carbon nanotubes is also developed. Monte Carlo simulations predict large low-field mobilities (0.4− 13 x10cm/V s) agreeing with experiments. The simulations also predict high electron drift velocities (5X10cm/s) and negative differential resistance. ELECTRON TRANSPORT SIMULATIONS AND BAND STRUCTURE CALCULATIONS OF NEW MATERIALS FOR ELECTRONICS: SILICON CARBIDE AND CARBON NANOTUBES