Ab-initio high-field transport and noise in p-Si: low temperatures and high frequencies

The cryogenic transport properties of hot holes in silicon exhibit several anomalies, including an additional saturated drift velocity regime and a non-monotonic trend of the microwave-frequency current noise versus electric field. Despite prior investigations, these observations lack generally accepted explanations. Here, we examine the microscopic origin of these phenomena by extending the ab-initio theory of high-field transport and noise in semiconductors. We find that the drift velocity anomaly may be attributed to scattering dominated by acoustic phonon emission, leading to an extra regime of drift velocity saturation at low temperatures; while the non-monotonic trend in the current noise arises due to the decrease in momentum relaxation time with electric field. The former conclusion is consistent with the findings of a prior work, but the latter distinctly differs from previous explanations which invoked energy relaxation as the origin. This work highlights the use of high-field transport and noise phenomena as sensitive probes of microscopic charge transport phenomena in semiconductors.