Influence of structural and doping parameter variations on Si and $$\hbox {Si}_{1-x}$$ Si 1 - x $$\hbox {Ge}_{x}$$ Ge x double gate tunnel FETs: An analysis for RF performance enhancement

Abstract

This paper deals with the effect of structural and doping parameter variations on RF parameters for Si and $$\hbox {Si}_{1-x}\hbox {Ge}_{x}$$ -based double gate (DG) tunnel FETs (TFETs). For the first time, asymmetric gate oxide is introduced in the gate-drain overlap and compared with that of DG TFETs. The DC parameter subthreshold swing (SS) and RF parameter metrics, unity gain cut-off frequency ( $$f_{\mathrm{t}}$$ ) and maximum oscillation frequency ( $$f_{\mathrm{max}}$$ ) are extracted by varying structural parameters, gate length ( $$L_{\mathrm{g}}$$ ), gate oxide thickness ( $$t_{\mathrm{ox}}$$ ), channel thickness ( $$t_{\mathrm{ch}}$$ ), doping parameters, channel doping ( $${{N}}_{\mathrm{ch}}$$ ), drain doping ( $$N_{\mathrm{d}}$$ ) and source doping ( $$N_{\mathrm{s}}$$ ) in and around their nominal value. For a channel thickness of 15 nm, a very less SS of 8 mV / dec is achieved in $$\hbox {Si}_{1-x}\hbox {Ge}_{x}$$ -based DG TFETs with gate-drain overlap. Variations of gate oxide thickness offer better RF performance enhancement for Si-based asymmetric gate oxide devices. This could be achieved because of the higher tunnelling rate of electrons occurring at the source side of asymmetric gate oxide devices.