Photoresponse of a p-type Si field emitter

Enhancement of electron emission by illumination of a gated single-tip p-type field emitter was studied using a GaAlAs pulse laser. The increase of the emission current under the illumination is proportional to the emission current without laser at low gate voltages and tends to saturate with increase of the gate voltage. A modulation electron beam is generated directly from the emitter by the pulse laser. The rise time of the photoresponse in the emitter is al least less than 4 μs. On the other hand, the fall time of the photoresponse is about 40 μs, which is determined by the diffusion process of the electrons photogenerated outside the depletion layer in the emitter.