Electrical and luminescent properties and deep traps spectra in GaN nanopillar layers prepared by dry etching

Electrical properties, microcathodoluminescence spectra, and spectra of deep traps were studied for nanopillar structures prepared by dry etching of undoped GaN films using natural masks formed by Ni nanoparticles. It is shown that as-prepared nanopillar structures have low bandedge intensity, very high leakage current of Schottky diodes, their electrical properties are determined by 0.2 eV electron traps or, after etching in aqua regia, 0.14 eV electron traps that are commonly associated with radiation defects. Deep levels transient spectroscopy spectra measured after aqua regia etching are dominated by 1 eV electron traps, other common radiation defects. Annealing at 600 degrees C is instrumental in eliminating the 0.2 eV and 0.14 eV electron traps, but not the 1 eV traps. A higher temperature annealing at 900 degrees C is required for strongly suppressing the latter and increasing the bandedge luminescence peak magnitude by 2 times compared to control sample. The best results in tems of luminescence efficiency increase are produced by additional etching in aqueous solution of KOH, but subsequent etching in aqua regia is necessary to suppress excessive surface leakage due to surface contamination by the KOH treatment. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757942]