Effects of space charge on the current-voltage characteristics of field emitter arrays

Abstract

Field emitter arrays are microfabricated very high electron current density sources. For rf amplifier applications, typical current densities are typically on the order of 100 Amps/cm2. Unlike thermionic emitters, the current densities at the emission sites on field emitters can approach 108 Amps/cm2 at high fields. Consequently, the high current from the array can affect the I(V) characterization of the emitters. In this manuscript, we use a simple model of a field emitter to calculate the one dimensional space charge effects on the current versus gate voltage characteristics. Two effects are treated: charge between the gate and anode, and charge within the FEA unit cell, which gives rise to a new space charge component. It is shown that space charge effects can taint the Fowler Nordheim parametrization of field emitters and consequently affect the estimates of their transconductance.