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Published online by Cambridge University Press: 01 February 2011
P- and n-type conductivity domains in dual-doped ZnO:As+N layers grown by metal organic vapor phase epitaxy on GaN/sapphire templates were electrically microcharacterized by scanning capacitance (SCM) and scanning surface potential microscopy (SSPM) techniques with respect to their defect states. The p-type domains were found to be dominated by two acceptors with thermal activation energies of about 80 and 270 meV as observed by transient SCM scans at different temperatures. Optically excited SSPM scans revealed defect-to-band-transitions at 400, 459, and 505 nm omnipresent in both domain types as well as a shallower transition at 377 nm exclusively in the p-type regions. According to the similar energy levels the optical transitions at 377 and 400 nm are assigned to acceptor states, whereby the 80meV-acceptor is probably responsible for the conversion from n- to p-type in the domains.