Investigation on the formation mechanism of p-type ZnO:In-N thin films: experiment and theory

Effects of post-annealing on electrical properties of N+ ion-implanted into indium doped ZnO (ZnO:In-N) films are investigated. p-type conduction of ZnO:In-N films with the appropriate annealing have been confirmed by Hall-effect measurements and electrical rectification behavior of homojunctions. The transmitted spectra and temperature-dependent photoluminescence (PL) spectroscopy results show that the band gap of p-type ZnO:In-N is narrow as compared to ZnO:In and the ionization acceptor energy is estimated to be 128meV, which agrees well with our calculated transition levels epsilon mml:mfenced close= open=0/-1 mml:mfenced of In-Zn-2N(O). X-ray photoelectron spectroscopy (XPS) spectra confirm the dominant existence of N-related acceptor defect complexes in p-type samples. Combining with transition state calculations, we find that the incorporation of In can facilitate p-type effective doping by pinning a passive impurity band above the valence band maximum (VBM) and decreasing thermal activation energy of N interstitial (N-i) in ZnO.