Improved electrical and RF performance of a junctionless vertical super-thin body (VSTB) FET by increased substrate doping

Abstract

This article focuses on the incorporation of a junctionless (JL) body in a newly invented structure called vertical super-thin body (VSTB) FET and performance evaluation of the JL VSTB FET in terms of different substrate doping (Ns) through a properly calibrated Sentaurus TCAD tool. Compared to the inversion mode device, its JL counterpart significantly decreases off-state leakage current (Ioff) by more than two orders of magnitude and improves subthreshold swing (SS) by 36.69 mV/dec. More importantly, the strong control of Ns on the electrical and radio-frequency (RF) characteristics of the device is explored at a fixed body doping and gate work-function. This study reveals that Ns-increase highly suppresses short channel effects by increasing the body depletion charges and thereby decreasing the channel electron density. An excellent improvement of more than three orders of magnitude is observed in both Ioff and Ion/Ioff ratio for a change of Ns from 1016 to 1019 cm−3. Such an Ns-increase also decreases SS and drain-induced-barrier-lowering by 102.26 mV/dec and 60.34 mV/V, respectively. Various RF parameters such as transconductance, input capacitance, gate-drain capacitance, unity-gain cut-off frequency, and gain-bandwidth-product also exhibit impressive improvement for higher Ns. This study is expected to help future research on such a new device as VSTB FET by revealing the attractive substrate doping control on the device electronics.