Fabrication of p-n junctions in ZnO by arsenic ion implantation followed by annealing in atomic oxygen

We report the properties of p-n junctions produced in ZnO films by As+ ion implantation followed by annealing in atomic oxygen. The starting films, n-ZnO Ga , were grown by magnetron sputtering on amorphous SiO2 substrates. As shown by x-ray diffraction, the c axis of ZnO is perpendicular to the film surface. The resistivity of the p-ZnO As layer is 30-35 Omega cm, carrier mobility 1-2.5 cm(2)/(V s), and hole concentration 3 x 10(18) cm(-3). The arsenic and gallium concentrations are 2.5 x 10(19) and 1 X 10(18) cm(-3) respectively. The arsenic profile is Gaussian in shape, as shown by secondary ion mass spectrometry. Current-voltage data attest to the presence of an i-layer and to recombination in the space charge region. The barrier height evaluated from current-voltage and capacitance-voltage data is about 3.4 eV, which is comparable to the band gap of ZnO. The electro- and photoluminescence spectra of the junctions show bands at 440 and 510 nm. The 510-nm emission is typical of as-grown n-ZnO Ga films. The 440-nm band is attributable to donor-acceptor recombination.