Nitrogen acceptors in bulk ZnO (000(1)over-bar)) substrates and homoepitaxial ZnO films

Bulk single crystals of unintentionally doped ZnO having charge carrier concentration, N-D-N-A values of similar to 10(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 similar to 8x10(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.