Defects in a nitrogen implanted and thermally annealed zinc oxide thin film (n-type conducting) and reference samples were studied. Space charge regions realised by the fabrication of semi-transparent palladium Schottky contacts permitted the application of capacitance spectroscopic methods and photocurrent measurements. The formation of a deep level labelled TN1 was reported. It was 580meV below the conduction band edge, probably related to nitrogen, and had to be distinguished from the well-known intrinsic deep-level E4 at almost the same energetic depth. Capacitance measurements in combination with optical excitation, conducted at various temperatures, as well as photo-current measurements, revealed the existence of two states approximately 60 and 100meV above the valence band edge in nitrogen-implanted samples. These states caused a degree of acceptor compensation which was larger than 0.9. The thermal emission of holes from these states into the valence band was observed using optical deep-level transient spectroscopy.

Defects in a Nitrogen-Implanted ZnO Thin Film. M.Schmidt, M.Ellguth, F.Schmidt, T.Lüder, H.Wenckstern, R.Pickenhain, M.Grundmann, G.Brauer, W.Skorupa: Physica Status Solidi B, 2010, 247[5], 1220–6