AC Impedance Compared to DC Characterization for Source-Drain Resistance in Junctionless Gate-All-Around MOSFETs

This study investigates the frequency-dependent AC source-drain impedance (ZDS) in p-type junctionless gate-all-around (JLGAA) MOSFETs, and compares it to the DC source-drain resistance (RDS) under various biasing and stress conditions. The analysis focuses on how RDS and ZDS respond to different gate voltages, providing insight into their influence on device performance. While RDS is extracted from the ohmic region of conventional ID-VD measurements, ZDS is obtained directly using impedance analysis to capture frequency-dependent behavior. Results reveal that during turn-on, RDS is slightly lower than ZDS, although ZDS retains a mainly resistive profile. However, after reliability stress and near the quasi turn-off regime, a more pronounced divergence between RDS and ZDS is observed. This is attributed to reduced channel conductivity and increasing frequency-dependent effects. At higher reverse gate bias, ZDS exhibits noticeable capacitive behavior due to enhanced channel depletion, and this effect becomes more significant as the channel length increases. These findings highlight the critical role of ZDS in assessing the dynamic performance of JLGAA FETs. Unlike static RDS characterization, frequency-sensitive impedance measurements offer deeper insight into AC behavior, supporting more accurate modeling and optimization under time-varying or transient operating conditions.