Low Temperature Performance of Deep Submicron Germanium pMOSFETs

The electrical characteristics of germanium (Ge) pMOSFETs with high-κ dielectric and gate lengths down to 125nm have been studied as a function of temperature down to 77K. The effective hole mobility improves from 235cm2/Vs at room temperature to 490cm2/Vs at 77K due to the reduction of phonon scattering. We report a drive current enhancement of 1001 μA/μm at 295K to 1394μA/μm at 77K for L = 125nm and VG - VT = VD = -1.5V and a reduction in the off-current by 1-2 decades. The decrease in the subthreshold slope from 100mV/dec to 37mV/dec at 77K would allow power supply voltage scaling, further reducing the off-state current, and making Ge transistors suitable candidates for low temperature CMOS applications.