Hole mobility enhancements and alloy scattering-limited mobility in tensile strained Si/SiGe surface channel metal–oxide–semiconductor field-effect transistors

Strained Si-based metal–oxide–semiconductor field-effect transistors (MOSFETs) are promising candidates for next-generation complementary MOS (CMOS) technology. While electron mobility enhancements in these heterostructures have been thoroughly investigated, hole mobility enhancements have not been explored in as much detail. In this study, we investigate the dependence of hole mobility in strained Si MOSFETs on substrate Ge content, strained layer thickness, and channel composition. We show that hole mobility enhancements saturate at virtual substrate compositions of 40% Ge and above, with peak mobility enhancements over twice that of coprocessed bulk Si devices. These results represent peak hole mobilities above 200cm2/V-S. Furthermore, we demonstrate that hole mobility in strained Si/relaxed Si0.7Ge0.3 heterostructures displays no strong dependence on strained layer thickness, indicating that strain is the primary variable controlling channel mobility in strained Si p-type MOSFETs (p-MOSFETs). We then ...