Germanium p-channel MOSFET's with high channel mobility, transconductance, and k-value

Abstract

The authors report p-channel germanium MOSFETs which exhibit channel mobilities more than four times higher than typically obtained in p-channel silicon devices (in excess of 1000 cm/sup 2//V-s with a gate dielectric thickness of approximately 220 AA). Fabrication of these MOSFETs is quite straightforward and utilizes equipment which is comparable to that used for conventional silicon MOSFET processing. Germanium p-channel MOSFETs having effective channel lengths down to approximately 2.3 mu m (2.75- mu m gate length) have been fabricated. Using a dielectric capacitance of 2.5*10/sup -7/ F-cm/sup -2/ taken from large area devices, a mobility of approximately 1050 cm/sup 2//V-s can be inferred from the slope of the transconductance curve. For the 2.3- mu m device, a transconductance of 50 mS/mm at approximately 0.5 V above threshold and a k-value of 110 mS/V-mm have been obtained. This performance is significantly better than that of p-channel silicon devices having similar channel length and approximately 220-AA gate dielectric thickness.