Effects of surface condition on the work function and valence-band position of ZnSnN2

ZnSnN 2 is an emerging wide band gap earth-abundant semiconductor with potential applications in photonic devices such as solar cells, LEDs, and optical sensors. We report the characterization by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy of reactively radio-frequency sputtered II–IV-nitride ZnSnN 2 thin films. For samples transferred in high vacuum, the ZnSnN 2 surface work function was 4.0 ± 0.1 eV below the vacuum level, with a valence-band onset of 1.2 ± 0.1 eV below the Fermi level. The resulting band diagram indicates that the degenerate bulk Fermi level position in ZnSnN 2 shifts to mid-gap at the surface due to band bending that results from equilibration with delocalized surface states within the gap. Brief (