International Conference on Solid State Devices and Materials

Direct-bandgap germanium-tin (GeSn) is a promising material owing to its high carrier mobility for high-performance logic devices. In this work, we investigate electron transport properties in Ge(Sn) n-type metal-oxide-semiconductor field-effect transistors (MOSFETs) with a Sn fraction up to 8 % at temperatures from 300 K to 4 K. For the Ge and Ge_0.96Sn_0.04 n-MOSFETs, the electron mobility decreases as the temperature decreases while the electron mobility of the Ge_0.92Sn_0.08 device is almost constant at 300 K ~ 4 K. We attribute this to an increased electron population in the direct Gamma-valley owing to the transition of indirect-bandgap to direct-bandgap GeSn at a Sn fraction ~ 8 %.