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A study of the photoelectrochemical etching of n-GaN in H3PO4 and KOH electrolytes
Date
2019
Abstract
We investigated the photoelectrochemical etching of n-GaN in H3PO4 and KOH as a function of electrolyte concentration, potential and light intensity. Etch rates measured by stylus profilometry were compared with coulometric and amperometric values. In both electrolytes, etch rates increased with concentration, reaching a maximum at 3.0 mol dmâ 3 and decreasing at higher concentrations.The increase in etch rate with concentration of either H3PO4 or KOH reflects the amphoteric nature of gallium and the decrease above 3.0 mol dmâ 3 is attributed to common-ion effects. Profilometric etch rates were lower than coulometric and amperometric etch rates reflecting formation of a surface film. SEM and profilometry demonstrated that thick surface films are formed at lower concentrations. Etch rates increased linearly with light intensity indicating a carrier-limited etching regime: a quantum efficiency of 57.6% was obtained. At light intensities greater than â ¼35 mW cmâ 2 the etch rates showed evidence of saturation. AFM and SEM images of the etched GaN surfaces showed a distinctive ridge-trench structure with a hexagonal appearance. Photoluminescence spectra of the etched GaN show a significant increase in the defect-related yellow luminescence peak suggesting correlation to the formation of the ridge structures, which may represent dislocations terminating at the surface
Supervisor
Description
peer-reviewed
Publisher
Electrochemical Society
Citation
ECS Journal of Solid State Science and Technology;2020 9, 015003
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Heffernan_2019_AStudy.pdf
Adobe PDF, 1.72 MB