Numerical study of Bloch electron dynamics in wide band-gap semiconductors

Abstract

In this paper, we are using numerical calculations to demonstrate the importance of band to band tunneling in wide band-gap semiconductors. We have considered 4H–SiC, 3C–SiC and wurtzite GaN as prototype semiconductors in the demonstration. Wide band-gap semiconductors allow device operation under very high-applied electric fields, where significant band to band tunneling is expected to occur. Hexagonal wide band-gap semiconductors have a valence band structure with a large number of bands separated by rather small energies. Our calculation shows that this leads to a very significant band to band tunneling even at relatively low electric fields. In cubic wide band-gap semiconductors the tunneling is much less pronounced. However, at the valence band maximum the band separations are small enough to allow significant band to band tunneling. The spin–orbit interaction tends to bend the band near the maximum creating degradation from a parabolic curvature. This bending is found to significantly influence the band to band tunneling process.