Sputter deposited GeSn alloy: A candidate material for temperature sensing layers in uncooled microbolometers

Abstract

In this paper, we study the resistance versus temperature characteristics of Ge1-xSnx thin film alloys to assess the possibility of using them for temperature sensing layers in microbolometers. Ge1-xSnx thin films, with 200 nm thicknesses, are deposited at room temperature using simultaneous RF and DC sputter deposition from Ge and Sn targets. Accordingly, Ge1-xSnx thin films with different Sn concentrations were prepared. Atmoic force microspcopy (AFM) analysis is performed showing rms surface roughnesses less than 0.56 nm for all the prepared Ge1-xSnx thin films. Sheet resistance versus temperature measurements are made revealing temperature coefficients of resistances (TCRs) of −3.96, −3.63 and −3.29%/K at resistivity values of 164.6, 69.14, and 45.46 Ω∙cm for Sn concentrations of 17%, 22% and 25% respectively. This study shows that the Ge1-xSnx material can be considered as a potential candidate towards high performance low cost uncooled microbolometers.