INFLUENCE OF SERIES RESISTANCES AND INTERFACE COUPLING ON THE TRANSCONDUCTANCE OF FULLY-DEPLETED SILICON-ON-INSULATOR MOSFETS

A model is proposed to describe the variation of the transconductance in fully-depleted silicon on insulator MOSFETs as a function of the front/back gate biases, channel length and series resistances. The influence of series resistances on the static characteristics of short-channel transistors depends on the region of operation, via the front and back gate voltages, and is a maximum when both interfaces are inverted. Simple analytical expressions explain the gradual deformation of the transconductance curve and the lowering of the transconductance peak with increasing series resistances. The model is experimentally verified by associating external resistors to the transistor. It is shown that a major consequence of X-ray irradiations in short-channel SIMOX MOSFETs is the trapping of positive charges in the buried oxide, which causes activation of interface coupling effects and enhanced influence of series resistances.