Physically Based Evaluation of Effect of Buried Oxide on Surface Roughness Scattering Limited Hole Mobility in Ultrathin GeOI MOSFETs

This paper presents a numerical simulation study investigating the effect of buried oxide on surface roughness scattering limited hole mobility (μSR) in ultrathin germanium-on-insulator (GeOI) MOSFETs, for the first time. The simulation considers wave function penetration at channel/oxide interface and nonlinear dependence of scattering matrix element on surface fluctuation. Three types of buried oxide materials are compared (GeO<;sub>2<;/sub>, SiO<;sub>2<;/sub>, and Si<;sub>3<;/sub>N<;sub>4<;/sub>). The μSR increases in the order of SiO<;sub>2<;/sub> <; GeO<;sub>2<;/sub> <; Si<;sub>3<;/sub>N<;sub>4<;/sub>. This dependence of μSR on buried oxide material is due to surface fluctuation scattering from backside Ge/buried oxide interface. Our simulation results show that Si<;sub>3<;/sub>N<;sub>4<;/sub> and GeO<;sub>2<;/sub> are beneficial as buried oxide for mobility enhancement in GeOI MOSFETs, compared with conventional SiO<;sub>2<;/sub> as buried oxide. Our findings provide an insight into further improving mobility characteristic.