The impact of quantum confinement on the electrical characteristics of ultrathin-channel GeOI MOSFETs

The impact of quantum confinement on the electrical characteristics of ultrathin-channel GeOI n-MOSFETs is investigated on the basis of the density-gradient model in TCAD software. The effects of the channel thickness (T-ch) and back-gate bias (V-bg) on the electrical characteristics of GeOI MOSFETs are examined, and the simulated results are compared with those using the conventional semi-classical model. It is shown that when T-ch > 8 nm, the electron conduction path of the GeOI MOSFET is closer to the front-gate interface under the QC model than under the CL model, and vice versa when T-ch < 8 nm. Thus the electrically controlled ability of the front gate of the devices is influenced by the quantum effect. In addition, the quantum-mechanical mechanism will enhance the drain-induced barrier lowering effect, increase the threshold voltage and decrease the on-state current; for a short channel length (<= 30 nm), when T-ch > 8 nm (or < 8 nm), the quantum-mechanical mechanism mainly impacts the subthreshold slope (or the threshold voltage). Due to the quantum-size effect, the off-state current can be suppressed as the channel thickness decreases.