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Bulk single crystals of unintentionally doped ZnO having charge carrier concentration, N D − N A values of ϳ10 17 cm −3 were implanted with N + ions at dosages of 10 15 and 10 16 cm −2 at 95 keV to a depth of 150 nm. The resulting p − n structure having acceptor concentrations ranging from 10 17 to 10 18 cm −3 was compared with nitrogen doped homoepitaxial films with ϳ8 ϫ 10 17 cm −3 acceptors. Photoluminescence spectra acquired at 8 K showed an increase in the peak for the neutral donor-bound to acceptor-bound transition at 3.210 eV with increasing annealing temperature, thermal activation of a unique donor to acceptor transition due to nitrogen at 3.067 and 3.057 eV for implanted and epitaxial films, respectively; and an increase in the intensity of the defect-related green band at selected temperatures. Electroluminescence measurements at 300 K revealed an ultraviolet band, direct band-to-band recombination at 3.34 eV, donor-acceptor pair recombinations at 3.19 and 3.0 eV, and recombination in the green region centered at 2.49 eV. Current-voltage characteristics of implanted and homoepitaxial p − n diodes were also determined.

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ZnO has distinct advantages over competing technologies such as GaN. Two advantages are the inherent improvement in ultraviolet (UV) brightness, necessary for the biological sensor application where the signal-to-noise ratio (SNR) is enhanced by a bright UV source, and the second is the availability of ZnO lattice-matched substrates, which will result in lower defect densities than GaN, higher manufacturing yield, and then lower cost. The ZnO material system's advantage in exciton binding energy of 60 MeV, a three-time improvement over GaN, will result in UV emitters with superior performance. 1