Optimized Ge channel profiles for VLSI compatible Si/SiGe p-MOSFET's

Theoretical and experimental support is provided to demonstrate that, with the design constraint of a fixed Ge dose, the effective hole mobility and carrier confinement in SiGe MOSFET's are maximized by employing positively graded triangular Ge profiles in the channel. Hole mobilities in excess of 400 cm/sup 2/Vs were obtained experimentally for transistors with 0-50% triangular Ge channel profiles. When compared to devices with rectangular Ge profiles, the MOSFET's with triangular profiles demonstrated 30-40% improvement in mobility, transconductance and cutoff frequency. These results were observed for both MBE- and CVD-grown wafers.<>