Hole Mobility Boost of Ge p-MOSFETs by Composite Uniaxial Stress and Biaxial Strain

Abstract

The hole mobility of relaxed Ge channel, and strained Ge channel on relaxed Si0.6Ge0.4 substrate were simulated and compared to our experimental work (Al2O3/GeO2 gate stack) and previous data. The rougher interface at GeO2/Ge than SiO2/Si makes a faster roll-off of Ge hole mobility at high field. For SiO2/Ge interface, the Ge hole mobility has a similar roll-off as Si universal mobility. Ge has higher mobility enhancement than Si under uniaxial compressive stress along [110] direction. For composite uniaxial compressive stress (-3GPa) and biaxial compressive strain (2.4%) on Ge p-MOSFETs, Ge mobility enhancement can reach as high as 23 times of Si mobility. The mass reduction of Ge is mainly responsible for the mobility enhancement.