Experimental determination of minority electron mobility in p-type pseudomorphic SiGe/Si

The minority electron mobility in the p-type pseudomorphic SiGe layer has been measured. SiGe/Si n-p-n HBTs have been fabricated with MBE-grown wafers and their DC and RF characteristics were used for the estimation of the mobility by the cutoff frequency method. The measured room temperature minority electron mobility values were found to be 302.7 cm/sup 2//V.s and 90.9 cm/sup 2//V.s for Ge composition of 20% and 40%, respectively, at the doping concentration of 7/spl times/10/sup 19/ cm/sup -3/. The corresponding drift diffusion constants were 7.87 cm/sup 2//s and 2.37 cm/sup 2//s, respectively. The observed trend may be useful information for the optimization of SiGe/Si HBTs for high-speed operation.