TY - JOUR
T1 - A Study of the Photoelectrochemical Etching of n-GaN in H3PO4 and KOH Electrolytes
AU - Heffernan, C.
AU - Lynch, R. P.
AU - Buckley, D. N.
N1 - Publisher Copyright:
© The Author(s) 2019. Published by ECS..
PY - 2020
Y1 - 2020
N2 - 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 dm-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 dm-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 ∼35 mW cm-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.
AB - 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 dm-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 dm-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 ∼35 mW cm-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.
UR - http://www.scopus.com/inward/record.url?scp=85081952306&partnerID=8YFLogxK
U2 - 10.1149/2.0082001JSS
DO - 10.1149/2.0082001JSS
M3 - Article
AN - SCOPUS:85081952306
SN - 2162-8769
VL - 9
SP - -
JO - ECS Journal of Solid State Science and Technology
JF - ECS Journal of Solid State Science and Technology
IS - 1
M1 - 015003
ER -