Observation of valence band electron emission from n-type silicon field emitter arrays

Electron emission from the valence band of n-type Si field emitter arrays is reported. High electrostatic field at the surface of Si was achieved by reducing the radius of the emitter tip. Using oxidation sharpening, 1 mu m aperture polycrystalline Si gate, n-type Si field emitter arrays with small tip radius (similar to 10 nm) were fabricated. Three distinct emission regions were observed: conduction band emission at low gate voltages, saturated current emission from the conduction band at intermediate voltages, and valence band plus conduction band emission at high gate voltages. Emission currents at low and high voltages obey the Fowler-Nordheim theory. The ratio of the slopes of the corresponding Fowler-Nordheim fits for these two regions is 1.495 which is in close agreement with the theoretical value of 1.445. (C) 1999 American Institute of Physics. [S0003-6951(99)00932-8].