Field Emission from Surface States in Semiconductors

Abstract

The consequences of tunneling from surface states on the total energy distribution of field emitted electrons from a clean germanium surface have been investigated in some detail using a model for the surface states originally suggested by Handler. At low emitted current densities (<102 A·cm-2) the emitted electrons come mostly from the surface states and from the valence band. The shape of the calculated distribution is in reasonable agreement with available experimental data. At current densities of the order of 103 A·cm-2 emission from the conduction band becomes appreciable but it is still a small proportion of the emitted current. We expect that at higher current densities (<104 A·cm-2) corresponding to applied fields \\gtrsim0.5 Volts/Å the conduction band will eventually become degenerate at the surface. For these current densities however the transport of electrons and holes in the interior of the semiconductor play an important role and the theory in its present form becomes inapplicable.