Significant reduction in semiconductor interface resistance via interfacial atomic mixing

TL;DR

This study uses Green's functions to analyze how atomic mixing at Si/Ge interfaces significantly reduces contact resistance by increasing charge transmittance through nonspecular transmission channels, informing future heterostructure design.

Contribution

It demonstrates that atomic mixing at semiconductor interfaces enhances charge transport by opening nonspecular channels, reducing contact resistance, which was not well understood before.

Findings

Perfect interfaces have high contact resistance due to momentum mismatch.

Atomic mixing increases transmittance by creating nonspecular channels.

Disordered interfaces with certain symmetries further reduce resistance.

Abstract

The contact resistance between two dissimilar semiconductors is determined by the carrier transmission through their interface. Despite the ubiquitous presence of interfaces, quantitative simulation of charge transport across such interfaces is difficult, limiting the understanding of interfacial charge transport. This work employs Green's functions to study the charge transport across representative Si/Ge interfaces. For perfect interfaces, it is found that the transmittance is small and the contact resistance is high, not only because the mismatch of carrier pockets makes it hard to meet the momentum conservation requirement, but also because of the incompatible symmetries of the Bloch wave functions of the two sides. In contrast, atomic mixing at the interface increases the carrier transmittance as the interface roughness opens many nonspecular transmission channels, which greatly reduces the contact resistance compared with the perfect interface. Specifically, we show that disordered interfaces with certain symmetries create more nonspecular transmission. The insights from our study will benefit the future design of high-performance heterostructures with low contact resistance.