Light emission from interface traps in SiC MOSFETs

Images of light emission from electron-hole recombination in 4H and 6H SiC n-type MOSFETs were observed by alternately driving the channel between accumulation and inversion. Light emission is observed from recombination at interface traps and from the bulk under the channel. The yield of light from recombination at interface traps is an order of magnitude greater than the yield from the bulk. Low mobility and high interface trap density impedes the flow of electrons from the source and drain into the channel. The time evolution of this flow was imaged. The rate of the electron flow in 4H MOSFETs is much slower than in 6H MOSFETs due to the lower channel mobility and higher interface trap density in the former. Emission images also reveal extended defects in the channel region. Different extended defects were observed in 6H and 4H MOSFETs. The defects in the 6H devices altered the electron flow, but the defects in the 4H devices did not affect the electron flow.