Effects of tunneling on a-Si:H Schottky barriers

Schottky diodes have been prepared by depositing semitransparent metallic films (Pd, Cr, and Au) onto hydrogenated amorphous silicon (a-Si:H) grown by the glow-discharge method. The a-Si:H was n doped and undoped presenting different densities of gap states (Ns). Barrier heights Φb were measured by internal photoemission and correlated to Ns. The activation energies were also determined. The results are understood in terms of both thermionic-field-emission tunneling and resonant tunneling through localized states of the conduction-band tail. It is found that the latter tunneling effect has a remarkable influence on the experimentally determined value of Φb.