Optimization of junctionless stacked nanosheet FET - RF stability perspective

Radio frequency (RF) stability is an indispensable selection component to operate the device in RF range. An unstable device is susceptible to oscillating for any passive termination networks at input/output ports. In this article, the RF stability performance of junctionless stacked nanosheet FET (JL-SNSHFET) is deliberated by investigating the impact of its geometrical parameters, and ambient temperature (TA) on the performance of transit frequency (fT), maximum oscillation frequency (fmax), stability (K), forward current gain (h21) and unilateral gain (U) through extensive technology computer-aided design (TCAD) numerical simulations. It is discerned that the variations in nanosheet width (WNSH), thickness (tNSH), oxide thickness (tox), spacer thickness (tsp), and ambient temperature exert substantial influence on JL-SNSHFET RF stability performance. The increase in WNSH, tNSH, and TA confer the stability of JL-SNSHFET at low frequency due to enhanced effective width. Whereas, the increase in tox and tsp defers the stability of JL-SNSHFET to extended frequency. The proposed optimized device shows an improved fT of 200 GHz and fmax of 467 GHz. It is unconditionally stable for the frequencies above 175 GHz, without any auxiliary network for stabilization. The results presented in this work provide design guidelines for JL-SNSHFET for RF applications.