Chemical vapor deposition, characterization and device development of monocrystalline beta- and alpha(6hydrogen)-silicon-carbide thin films.

摘要

The principal objective of this dissertation research has been the epitaxial growth of beta-silicon carbide ({dollar}beta{dollar}-SiC) and, to a lesser extent, alpha(6H)-silicon carbide (6H-SiC) thin films on Si (100) and/or 6H-SiC substrates via the chemical vapor deposition (CVD) process. The as-grown thin films have been characterized in terms of crystal structure, surface morphology, defects, and electrical properties. In addition, Au Schottky diodes and MESFETs were fabricated.; Beta-SiC monocrystalline films grown on Si (100) substrates via CVD have been examined utilizing transmission electron microscopy (TEM). Numerous defects including; stacking faults, dislocations and antiphase domain boundaries (APBs), generated from {dollar}beta{dollar}-SiC/Si interface, were observed. Some of them extended throughout the entire epilayer up to the as-grown surface. Therefore, various off-axis Si (100) substrates were used to eliminate or reduce these defects. The results showed that the APBs were eliminated, and that stacking faults and dislocations which were not associated with the APBs still remained. Hall effect, differential capacitance-voltage measurements, TEM, scanning tunneling microscopy (STM), and optical microscopy have been utilized for the characterization of these films. The most important result is that the leakage current in the {dollar}beta{dollar}-SiC films on off-axis Si (100) substrates is greatly reduced.; In a further attempt to eliminate all types of defects in the SiC films, 6H-SiC {dollar}{lcub}0001{rcub}{dollar} substrates were used for the growth of {dollar}beta{dollar}-SiC thin flims. Cross-sectional TEM (XTEM) and high resolution TEM showed a perfect, {dollar}beta{dollar}-SiC/6H-SiC coherent interface. The defect density is dramatically reduced. However, x-ray topography and plan view TEM examinations identified double positioning boundaries (DPBs), as well as triangular defects, and their modifications, composed of intersecting stacking faults. The nucleation of DPBs has been studied, and the origin of the triangular defects has also been discussed.; High quality 6H-SiC films were grown on off-axis 6H-SiC {dollar}{lcub}0001{rcub}{dollar} substrates. TEM showed that essentially no defects were generated from the epilayer/substrate interface and that DPBs were eliminated. Au Schottky diodes fabricated on these films showed a lower leakage current than any of the SiC films grown previously.; Metal-semiconductor field-effect transistors (MESFETs) were fabricated in a {dollar}beta{dollar}-SiC thin film grown on a Si (100) substrate. The maximum transconductance obtained was 2.1 mS/mm. Saturation of the drain currents was achieved at room temperature. Furthermore, these MESFETs performed reasonably well to 623 K.