Deep level transient spectroscopy, current-voltage, and capacitance-voltage measurements are used to study interface traps in metal-on-bulk-ZnO Schottky barrier diodes (SBDs). c-axis-oriented ZnO samples were cut from two different vapor-phase-grown crystals, and Au- and Pd-SBDs were formed on their (0001) surfaces after remote oxygen-plasma treatment. As compared to Au-SBDs, the Pd-SBDs demonstrated higher reverse-bias leakage current and forward-bias current evidently due to higher carrier concentrations, which might have been caused by hydrogen in-diffusion through the thin Pd metal. The dominant traps included the well-known bulk traps E3 (0.27 eV) and E4 (0.49 eV). In addition, a surface-related trap, Es (0.49 eV), is observed but only in the Pd-SBDs, not in the Au-SBDs. Trap Es is located at depths less than about 95 nm and shows an electron capture behavior indicative of extended defects. A possible correspondence between trap Es and the well-known 2.45 eV green band is suggested by depth-resolved cathodoluminescence spectroscopy on the same samples, which reveals an increase in the intensity of this band within ∼ 100 nm of the Pd/ZnO interface.
Look, D. C.,
Dong, Y. F.,
Mosbacker, H. L.,
& Brillson, L. J.
(2008). Surface Traps in Vapor-Phase-Grown Bulk ZnO Studied by Deep Level Transient Spectroscopy. Journal of Applied Physics, 104 (6), 63707.