Variable-Channel Junctionless Poly-Si FETs: Demonstration and Investigation With Different Body Doping Concentrations

In this letter, tri-gate polycrystalline silicon variable-channel junctionless transistors (VC-JLTs), which consist of a counter-doped p-type body below an n± active device layer, are successfully demonstrated to show a better performance compared with conventional tri-gate nanosheet (NS) JLTs. Because the potential barrier between the n-channel and p-body in the VC-JLT can be controlled by the gate, the effective conduction channel behaves as a “variable” channel, in which the conduction thickness is thinner or thicker than the physical n⁺ thickness for the OFF or ON state, respectively. Consequently, the VC-JLT can turn OFF more efficiently due to the enhanced volume depletion and turn ON with a smaller series resistance owing to the augmented conduction volume. In addition, for the first time, the impact of the body doping concentration is investigated and the performance sensitivities of VC-JLTs in terms of I_ON, V_T, S.S., and DIBL are discussed with respect to the dopant redistribution. Furthermore, the quality factor (ION/S.S.) of the VC-JLT is also benchmarked with recently published poly-Si JLTs, showing that the proposed VC-JLT exhibits good S.S. and a record ION, which makes it as a promising device for 3-D integrated nanoelectronics.