Field emission current investigation of p-type and metallized silicon emitters in the frequency domain

We investigated two different field emitter arrays consisting of 10 \times10 p-type and 10 \times 10 undoped Au-coated high aspect ratio silicon tips. The I-V characterization of the p-type sample showed a pronounced saturation for voltages higher than 500 V and a maximum emission current of 39 nA. The metallized sample revealed a FN-like emission up to several \mu A. The metallized and the p-type sample operating below the saturation region showed high current fluctuations of \pm 16 %. Whereas, the metallized sample with current regulation and the p-type sample in the saturation yielded a current stability of \pm 0.4 % and \pm 0.3 %, respectively. Investigations in the frequency domain revealed the for field emission typical 1/f-noise. By operating in the saturation region (p-type sample) or using an emission current regulation (metallized sample) the noise level was reduced by at least 20 dB. Finally, the p-type sample was illuminated by a light emitting diode to increase and modulate the emission current in the saturation region. The emission current was increased by a factor of 3.7 to 145 nA. With this configuration we emulated an unstable emission behavior and evaluated the performance of our emission current regulation circuit.