Charge kinetics across a negatively biased semiconducting plasma-solid interface

TL;DR

This study models charge transport across a negatively biased germanium semiconductor in a plasma environment, revealing hot carrier conduction and challenging the adequacy of the perfect absorber model for such interfaces.

Contribution

It provides the first self-consistent calculation of ambipolar charge kinetics and current-voltage characteristics for a plasma-semiconductor interface with detailed spatial and energetic resolution.

Findings

Current is carried by hot carriers.

The perfect absorber model is inadequate for semiconducting interfaces.

Charge distributions are spatially and energetically resolved.

Abstract

An investigation of the selfconsistent ambipolar charge kinetics across a negatively biased semiconducting plasma-solid interface is presented. For the specific case of a thin germanium layer with nonpolar electron-phonon scattering, sandwiched between an Ohmic contact and a collisionless argon plasma, we calculate the current-voltage characteristic and show that it is affected by the electron microphysics of the semiconductor. We also obtain the spatially and energetically resolved fluxes and charge distributions inside the layer, visualizing thereby the behavior of the charge carriers responsible for the charge transport. Albeit not quantitative, because of the crude model for the germanium band structure and the neglect of particle-nonconserving scattering processes, such as impact ionization and electron-hole recombination, which at the energies involved cannot be neglected, our results clearly indicate (i) the current through the interface is carried by rather hot carriers and (ii) the perfect absorber model, often used for the description of charge transport across plasma-solid interfaces, cannot be maintained for semiconducting interfaces.