A Four-FET Method for Extracting Mobility in FETs Without Field Oxide

Many fabricated III-V MOSFETs have electrically thin field oxide (FOX) that leads to parasitic currents and parasitic capacitances. When extracting long-channel mobility of such devices using the conventional two-FET method, some of these parasitic components are not subtracted out. In this paper, we present a simple four-FET method for extracting long-channel mobility that works well even when the equivalent oxide thickness (EOT) of the FOX is equal to the EOT of the FET gate oxide.