Abstract
Porous p-type gallium nitride (GaN) films were successfully formed using 50 Hz operated 60 mA alternating current-assisted photo-electrochemical etching for 90 min in 1:0, 1:1, 2:1, and 1:2 volume ratios of sulfuric acid:methanol solutions. The formation of Ga-O-N passivation layer on GaN films etched in 1:1 and 1:2 solutions has served as a barrier to limit etching behavior of the films, leading to the formation of tiny pores, which attenuated emission intensities of E2(high) and A1(TO) phonon modes, and near band edge (NBE) photoluminescence in addition to an emergence of yellow emission band attributable to defects originating from Ga-O-N. The increase of H2SO4 content than that of CH3OH in the 2:1 solution that resulted in the formation of the largest pore size (87.1 nm) has however enhanced emission intensities of E2(high), A1(TO), and NBE without the detection of yellow emission band. Detailed explanation with regard to the pore formation accompanied with defects generation, strain changes and in-plane stress relaxation as well as corresponding effects on optical bandgap of the films has been systematically studied.
Published Version
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