EXPERIMENTAL CHARACTERIZATION OF ELECTRON-HOLE GENERATION IN SILICON-CARBIDE

Thermal generation in wide bandgap semiconductors can be observed by m onitoring the capacitance recovery transients of npn (or pnp) storage capacitors in which the middle layer is floating. In this article, we report a study of thermal generation in 4H and 6H silicon carbide (SiC ). Three generation mechanisms are identified: bulk generation in the depletion regions of the pn junctions, surface generation at the perip hery of the capacitors, and defect generation associated with imperfec tions in the material. All three generation mechanisms are thermally a ctivated. Bulk generation and surface generation have activation energ ies of approximately halfbandgap, while defect generation exhibits fie ld-induced barrier lowering resulting in an apparent activation energy less than half bandgap. Because the generation rate is extremely low, most measurements are conducted at elevated temperatures (250-350 deg rees C). However, we also describe a long-term measurement at room tem perature in which the 1/e recovery time appears to be in excess of 100 years.