Electrical Characteristics of Vertical GaN Nanowire Vacuum Field Emitter Devices

The electrical characteristics of simulated vertical gallium nitride (GaN) nanowire (NW) vacuum field emission diodes (VFEDs) and GaN NW vacuum field emission transistors (VFETs) with flat- and sharp-tip GaN NW field emitters (FEs) are presented by investigating their dependence on geometry and material parameters. For a flat-tip GaN NW VFED, the turn-on voltage (V
_TO
) was decreased by decreasing the GaN NW diameter ( D), the anode to emitter distance (d), the work function of the anode metal (φ
_M
), or by increasing the GaN NW height ( h). Variations in doping concentration (N
_D
) of the GaN NW do not impact V
_TO
. The sharp-tip GaN NW VFEDs exhibited decreased V
_TO
as the degree of sharpness ( d
_sh
) was increased from 0 to 0.5 μm. The saturation emitter current density (J
_sat
) was only affected by variations in N
_D
, and was increased for increased N
_D
. The transfer (I
_DS
- V
_GS
) characteristics of sharp-tip VFETs exhibited reduced threshold voltage (V
_TH
), increased transconductance (G
_{tm, max}
), and ON-/ OFF-current ratio, compared with the flat-tip ones. The output (J
_DS
- V
_DS
) characteristics of both types of devices showed nonlinear behavior at the low V
_DS
regime.