Vacuum field emission transistors with small gate-cathode overlapping areas: a simulation study

Vacuum field emission transistors (VFETs) are emerging as promising alternatives to the mainstream solid state electronic devices under some special hostile environments. Cutoff frequency ( f C ), which is jointly determined by gate-cathode capacitance ( C GK ) and transconductance ( g m ), is one of the key parameters of a VFET that is expected to work in high-frequency regimes. Several types of novel configurations, in which the gate-cathode coupling is intentionally weakened by either narrowing the gate or moving the gate away from the cathode, are put forward for the purpose of increasing f C . The transfer characteristics and the output characteristics of the VFETs with these novel configurations are studied by simulation. The simulation results show that narrowing the gates, as can be expected, leads to both smaller C GK s and smaller g m s in VFETs. Importantly, the reduction in C GK s is greater than that in g m in the newly proposed configurations. As a result, high f C are attainable under much lower voltages with the novel configurations.