Experimental and Analytical Characterization of Dual-Gated Germanium Junctionless p-Channel Metal–Oxide–Semiconductor Field-Effect Transistors

Abstract

The operation of germanium (Ge) dual-gated junctionless p-channel field-effect transistors (DG JL pFETs) is demonstrated. The top-gated hole mobility is approximately 120 cm2·V-1·s-1, which is close to the bulk mobility of p-type Ge with a doping concentration of 1019 cm-3. The mobility has a weak hole density dependence and increases by applying a negative bottom gate voltage. In addition, simple analytical expressions for both the current–voltage characteristics and the threshold voltage in the linear region of the DG JL pFET are described. The result shows that normally-off Ge DG JL pFETs are achievable. Furthermore, the threshold voltage variation due to the random dopant number fluctuations in the channel is also discussed, which indicates that it can be reduced by decreasing the Ge and oxide thicknesses.