Simulation of the electrical characteristics of field emission triodes with various gate structures

A new two-dimensional numerical simulation which can accurately reproduce the empirical electrical characteristics of vertical field-emission triodes (FET's) with various gate geometries has been developed. The electrical characteristics of volcano-shaped-gate FET's were simulated for the first time and compared with those of planar-gate ones. Volcano-shaped-gate FET's exhibit significant advantages over planar-gate ones due to their superior current-voltage ( I-V ) properties and larger tolerance of fabrication error. A reasonable definition of emission area was obtained by applying the non-uniform current density model. For sub-micron gate aperture, the gate current is obvious only if the device structure is deeply tip-recessed. On the basis of the evaluation of the device structures including the tip cone angle, the related tip-to-gate height, the emitter shape, and the shrinkage of gate aperture, a high-aspect-ratio conical emitter with a small tip radius will be the optimum structure of FET's for low-voltage operation.