Breakdown in conventional and vacuum microelectronics field emission devices

The purpose of this paper is to review the fundamental limits to stable field emitted current, starting from the simple case of field emitters of various materials in high vacuum conventional dimension devices, then going to VM devices with small and moderately compact FEAs (eg. 10⁶ tips/cm²), then finally to the very large and compact FEA (eg. 10⁵ tips and 10⁹ tips/cm²) used in some current microwave devices prototypes. In all cases we estimate the upper limits to current density and transconductance imposed by the onset of thermal instabilities. The observed occurrence of arcing at much lower current levels suggests, as a probable cause, an unusually large random fluctuation of the surface and emission of a field emission tip which in turn causes a temperature spike at the gate and initiates a runaway process in which both cathode and gate likely participate. Based on this assumption, we consider cathode and gate design techniques which may greatly reduce such fluctuations and thus allow arc free operation of FEAs at much higher current levels than now achieved