Structural and luminescent properties of ZnO:P films produced by annealing ZnP2 wafers in atomic oxygen

The epitaxial ZnO:P films are fabricated by annealing the ZnP2 wafers in atomic oxygen (oxygen radicals). The properties of the films are studied by X-ray diffraction analysis, atomic force microscopy, Auger spectroscopy, and photoluminescence measurements. In the X-ray diffraction spectra of the samples, the (002) peak is observed, suggesting that the ZnO:P films are oriented along the c axis. The Auger spectroscopy data show that the ZnO films contain phosphorus. The low-temperature photoluminescence spectrum observed for the ZnO: P films exhibits a 3.356 eV peak presumably corresponding to excitons bound at neutral acceptors and a peak at 3.306 eV (free electron)-acceptor transitions associated with the PO level. The phosphorus related acceptor level is localized at 128 meV above the top of the valence band. The origin of the 3.312 eV band related to recombination at donor-acceptor pairs is discussed.