Zinc nitride as a potential high-mobility transparent conductor

Polycrystalline and epitaxial zinc nitride (Zn3N2) films were grown by a reactive rf-magnetron sputtering technique. Phase-pure films were grown but XPS results indicated that a small amount of oxygen exists within all Zn3N2-xOx films. We prove experimentally that substitutional O on the N site (O-N(center dot)) can be treated as an electron donor. The electrical and optical properties can be tuned by tuning the x values. High mobilities were achieved in both polycrystalline and epitaxial Zn3N2 films. In-depth mobility analyses revealed both grain boundary scattering and ionization impurity scattering have main contribution to the electron transport in polycrystalline films, while neutral impurity scattering has negligible impact. The effective masses at the bottom of the conduction band were calculated to be (0.08 +/- 0.03)m(0), which is quite small. Such small electron effective masses contribute to lead to the high carrier mobility observed in Zn3N2. Optical bandgaps lie in a range from 2.2 to 2.7eV, which may be ascribed to interstitial N 2p in-gap state defects. We expect that zinc nitride with good transparency can be attained if the number of such defects is diminished. Our results in this work suggest that Zn3N2 is a potential choice for cost-effective transparent semiconductor devices with high mobility.