Silicon carbide (SiC) is currently under intensive investigation as a promising material for high temperature, high power and high frequency electronics and in radiation-hardened environments. However, the presence of various crystallographic defects (specifically micropipes, threading dislocations, both screw and edge as well as basal dislocations and stacking faults) in commercially available material limits the wide commercialization of SiC devices, since these defects affect device characteristics such as increase in reverse (leakage) current and forward voltage drop (degradation phenomena). Thus, it is important to identify the type of the defects and determine their density and distribution, and further understand the effect of specific defects on the performance of SiC devices.

The research presented in this dissertation is devoted to investigation and identification of crystallographic defects in SiC material influencing device performance of bipolar as well as unipolar structures. Special attention is paid to studying of crystallographic defects in bipolar diodes formed by diffusion, which is a novel approach for the formation of p-n junctions in SiC devices. The Electron Beam Induced Current (EBIC) mode of Scanning Electron Microscope in conjunction with other methods of defect investigation was used as the major tool for identification and analysis of the crystallographic defects.

The main contributions of this research are:

• Developed nondestructive method to identify specific dislocations (superscrew, screw, edge) in diffused p-i-n diodes using the EBIC technique.
• Demonstrated that micropipes and closed-core screw dislocations have dramatic effect on reverse current-voltage characteristics of diffused p-i-n diodes, that is similar to the effect of these defects on epitaxialy formed p-i-n diodes.
• Demonstrated for the first time that EBIC technique can be used for in-situ investigation of degradation phenomena in SiC bipolar devices. Particularly, the imaging and analysis of stacking faults as well as partial dislocation nucleation.
• Proposed that both C and Si core 30o partial dislocations in 4H-SiC have a comparable electrically activity. It is suggested that the nonradiative recombination rate significantly exceeds the radiative recombination rate on both the C and Si core 30o partial dislocations.
• Suggested that localized defects (for example clusters of carbon or B and Al atoms) can be nucleation sites for staking fault development and hence responsible for degradation of high power diffused p-i-n diodes.