Electron field emission from wide bandgap semiconductors under intervalley carrier redistribution

Electron field emission phenomena from semiconductors (and, in particular, wide band gap materials) are analyzed theoretically for the general case, i.e., by taking into consideration aspects that have not been considered earlier such as two (or more) valleys of the energy band structure, nondegenerated statistics for the free electrons, heating of conduction band electrons, intervalley carrier redistribution under applied electrical fields, size quantization of electron band spectra, and change in the field emission characteristics. Comparisons with experiments performed on the highly structured (micro- and nano) surfaces of the GaN wide bandgap semiconductor have been made. The influence of the above factors on the current-voltage Fowler-Nordheim characteristics was demonstrated by theory and experiment. From theoretical and experimental results the intervalley energy difference ( Δ E ) for GaN quantum-sized cathodes was estimated to be 0.8 eV, which is considerably less than that predicted for bulk semiconductor ( Δ E = 1.2 - 1.5 eV ) . Furthermore the field emission currents were several orders higher than for bulk material. This is in good agreement with the prediction of the proposed theoretical model.