Strained GeSn p-Channel Metal–Oxide–Semiconductor Field-Effect Transistors With In Situ Si2H6 Surface Passivation: Impact of Sn Composition

Abstract

We report a study about the impact of Sn composition on the performance of strained germanium-tin (GeSn) pMOSFETs. GeSn pMOSFETs with Sn compositions of 0.027, 0.040, and 0.075 were fabricated on Ge(001) with an in situ Si 2 H 6 passivation. Enhancement in drive current and transconductance is obtained for GeSn pMOSFETs with higher Sn composition due to the smaller capacitance equivalent thickness, the reduced source/drain resistance, and the improved effective hole mobility μeff. Right shift of threshold voltage with Sn composition is observed for the devices. Ge 0.973 Sn 0.027 , Ge 0.960 Sn 0.040 , and Ge 0.925 Sn 0.075 pMOSFETs demonstrate the peak μ eff of 340, 378, and 496 cm 2 /Vs, respectively. At an inversion charge density of 5 × 10 12 cm -2 , Ge 0.925 Sn 0.075 pMOSFETs demonstrate 36% and 24% enhancement in μ eff compared with Ge 0.973 Sn 0.027 and Ge 0.960 Sn 0.040 devices, respectively. Simulation shows that the enhancement in μeff with Sn composition is resulted from the reduction of hole effective mass and intervalley scattering between heavy and light holes caused by the increased compressive strain.