Simulation Of Field Emitter Vacuum Microtriodes

Vacuum triodes with field emitter array sources are examined to ascertain device performance characteristics. This is studied using the 2 &1/2 dimensional fully electromagnetic particle-in-cell code MAGIC, modified with a Fowler-Nordheim algorithm for the emitted current J = AE
²
exp(-BΦ
^3/2
/E). To avoid arbitrary truncation of the allowed angle of emission, the entire unit cell consisting of emission tip, gate structure and anode, is simulated simultaneously with the use of a highly nonuniform simulation mesh. Based upon the unit cell calculations, we obtain values for transconductance, cut-off frequency, de gain, and efficiency. A realistic device is being built by combining such cells into large arrays with micron scale spacings to obtain the required current densities. The transconductance per unit area which may be thus obtained exceeds the limits of conventional thermionic technology by several orders of magnitude. As the gain-bandwidth product depends upon the device's transconductance, such devices become of increased interest for RF amplification. As the current densities are increased however, the power deposition at a planar anode exceeds the material limits. Comparison with experimental results will be presented.