Bandstruwre dependence of impact ionisation in semiconductors from high pressure studies

Abstract

Abstract Hydrostatic pressure has been used to study the bandstructure dependence of impact ionisation in Si, GaAs and Ge photodiodes. The results were modeled using lucky drift and Monte Carlo calculations, with ionisation threshold energies calculated from model pseudopotential bandstructures. The results for Si, GaAs and Ge were significantly different, and were interpreted in terms of the different band structures. For Si, multiplication is dominated by electron ionisation in the A valleys due to the large intervalley separations. However for GaAs and Ge ionisation gives rise to final electron states which are not only in the lowest conduction-band valley as previously assumed, but throughout the Brillouin zone. This has important implications for our understanding of impact ionisation and for modelling of avalanche multiplication in semiconductor alloys and multilayers.