First-Principles Calculation of Alloy Scattering and n-type Mobility in Strained GeSn

TL;DR

This study uses first-principles calculations to analyze alloy scattering and electron mobility in n-type GeSn, revealing conditions for high mobility and effects of strain and composition.

Contribution

It provides the first detailed first-principles analysis of alloy scattering and mobility in GeSn alloys, including effects of strain and composition.

Findings

Mobility exceeds Ge at 13.5% Sn in unstrained GeSn.

Mobility can be over 25 times higher than Ge, reaching 10^5 cm^2/(Vs).

Strain and low Sn content significantly enhance mobility.

Abstract

We use first-principles electronic-structure theory to determine the intra- and inter-valley electron-alloy scattering parameters in n-type GeSn alloys. These parameters are used to determine the alloy scattering contributions to the n-type electron mobility of GeSn at $300K$ and $15K$ using a first iteration of the Boltzmann transport equation in the relaxation time approximation. For unstrained GeSn, we find that a Sn concentration of at least $13.5\%$ is needed to achieve an electron mobility greater than that of Ge. Our results show that the mobility of GeSn can be over $25$ times higher than the mobility of Ge, or $10^5$ cm$^2$/(Vs). At $15K$, less than $6\%$ Sn incorporation into Ge quadruples its mobility, which suggests GeSn has potential applications as a high mobility 2D electron gas. Applying biaxial tensile strain to GeSn further increases the mobility and at a lower Sn content than in unstrained GeSn.