Electron transport properties in high-purity Ge down to cryogenic temperatures

TL;DR

This study investigates electron transport in high-purity germanium at cryogenic temperatures using Monte Carlo simulations, revealing anisotropic velocities, negative differential mobility, and valley-dependent electron propagation.

Contribution

It provides a detailed simulation framework that accurately reproduces experimental electron velocities and explores electron behavior at millikelvin temperatures in germanium.

Findings

Simulated electron velocities match experimental data.

Identified anisotropic drift velocity and negative differential mobility.

Observed valley-dependent electron propagation patterns.

Abstract

Electron transport in Ge at various temperatures down to 20 mK has been investigated using particle Monte Carlo simulation taking into account ionized impurity and inelastic phonon scattering. The simulations account for the essential features of electron transport at cryogenic temperature: Ohmic regime, anisotropy of the drift velocity relative to the direction of the electric field, as well as a negative differential mobility phenomenon along the <111> field orientation. Experimental data for the electron velocities are reproduced with a satisfactory accuracy. Examples of electron position in the real space during the simulations are given and evidence separated clouds of electrons propagating along different directions depending on the valley they belong.