  Photoluminescence (PL) spectra of zinc oxide (ZnO) samples with different
hydrogen peroxide (H2O2) treatment durations were measured to examine several
point defects on the surface of the films. These results suggest successful
oxidation through the reaction between oxygen radicals dissociated from H2O2
and the ZnO surface. To further confirm the defect induced gain mechanism, we
fabricate highly transparent Schottky diodes, and measure the key diode
characteristics. Photocurrents are measured under different wavelengths, and
possible explanations of the high optical gain within the ultraviolet (UV)
region are provided.
