Revealing Low Thermal Conductivity of Germanium Tin Semiconductor at Room Temperature

Abstract

The low thermal conductivity of a material is a key essential parameter for its potential application in high‐performance thermoelectric devices. Unprecedently low thermal conductivity of germanium tin (Ge1−xSnx) semiconductor thin film is experimentally obtained at room temperature. The thermal conductivity decreases with increasing Sn concentration in the relaxed Ge1−xSnx binary alloy, which is explained mainly by increasing the interatomic distance between atoms via alloying. A pronounced decrease of thermal conductivity, by over 20 times, from 58 W m−1K−1 in Ge to ≈2.5 W m−1K−1 in relaxed Ge1−xSnx, with Sn content up to 9% is observed. This thermal conductivity is just ≈2 times higher than that of the state‐of‐the‐art thermoelectric material, Bismuth Selenium Telluride. Ge1−xSnx, in contrast, is a non‐toxic Group‐IV semiconductor material, that is epitaxially grown on a standard silicon wafer up to 300 mm diameter using the semiconductor industry standard epitaxial growth technique. As a result, it can lead to the creation of a long‐awaited high‐performance low‐cost thermoelectric energy generator for room‐temperature applications in human's daily life and would make a substantial contribution toward global efforts in CO2 emission‐free and green electricity generation.