Influence of structural and doping parameter variations on Si and $\hbox {Si}_{1-x}$ $\hbox {Ge}_{x}$ 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.