High-Mobility GeSn n-Channel MOSFETs by Low-Temperature Chemical Vapor Deposition and Microwave Annealing

A Ge 0.955 Sn 0.045 nMOSFET with a record high mobility of 440 cm 2 /V $\cdot $ s is demonstrated in this letter by a gate-first process. By low-temperature chemical vapor deposition, high-quality GeSn films were epitaxially grown. The ambipolar leakage is effectively suppressed by the low-thermal-budget microwave annealing (MWA) step. Furthermore, the peak mobility in the device after the MWA step is enhanced by a factor of two compared with those after rapid thermal annealing. This can be attributed to the weaker Coulomb scattering at the oxide interface after the MWA step, suggesting that MWA is effective for dopant activation and a better oxide interface quality at the same time.