Low leakage current optically gated silicon field emitter arrays

Gated silicon emitters (50×50 emitters at 20 μm spacing) having a “volcano” shape were fabricated by a dry etching-based technique. The insulating oxide layers formed by wet oxidation and low pressure chemical vapor deposition were ∼1 μm thick, and the Cr/Au film was deposited to function as the gate electrode. Quantum efficiency and dynamic range of photoenhanced field emission from gated silicon field emitter arrays improve at the expense of higher dark current (current with no photoexcitation) as the gate voltage is increased. For 830 nm photoexcitation, efficiency approached 29% at 130 V, and ratio of photocurrent to dark current peaked at 5.5 at 80 V. Measured saturation behavior was attributed to screening of the applied field by photogenerated electrons. Optical excitation with ∼10 ns pulses at 1064 nm revealed shorter anode current pulses at increasing gate bias consistent with an increase in collected drift electrons due to an increase in depletion layer thickness. Also, the ratio of anode current to gate current reached a high of 820 at 30 V.