Photoelectrochemical etching of InxGa1−xN

Abstract

Photoelectrochemical (PEC) etching of InxGa1−xN in the KOH solution under illumination of a Hg-arc lamp is studied. An indium oxide surface layer is formed during PEC etching, which slows down the etching rate. The PEC etch rate of InxGa1−xN is determined by dissolution of indium oxides into the solution. Increase of the solution temperature results in an increase of solubility of indium oxides and thus enhances the PEC etch rate. It is found that stirring the solution can accelerate indium oxides to dissolve into the solution and increase the etch rate. The thick indium oxide layer on the PEC-etched InxGa1−xN surface can be effectively removed by the treatment of using a hot 6N HCl solution. A post-treatment by using a 3.2 M KOH solution can provide a smooth sidewall on the PEC-etched surface for the potential application to laser cavity.

Anisotropy and Mechanistic Elucidation of Wet‐Chemical Gallium Nitride Etching at the Atomic Level

“…For instance, diffusion limitation has been reported under PEC conditions. [ 17,27,28 ] It is possible that the reaction mechanism changes once holes are generated by above‐bandgap illumination. Further experiments regarding the reaction mechanism should include a detailed study of the transition between NH 3 formation and N 2 /H 2 formation.…”

“…GaN reacts under dissociative water adsorption once it is immersed in aqueous KOH. [ 17 ] Protons bond to the negatively charged nitrogen, whereas the Ga‐polar surface is terminated by hydroxide ions. The schematic surface states of both polarities are shown in Figure , where the GaN, GaO, OH, and NH bond lengths are pictured to scale with the literature values of 1.96, 1.92, 0.98, and 1.01 Å, respectively.…”

“…Under different process conditions, a different mechanism is conceivable: the field of photoelectrochemical (PEC) etching entails application of above‐bandgap illumination and bias voltage. [ 17 ] Light illumination generates electron–hole pairs. The use of positive polarization also increases the availability of holes generated by illumination to support the oxidation partial reaction.…”

Wet‐Chemical Etching of GaN: Underlying Mechanism of a Key Step in Blue and White LED Production

“…Hwang and co‐workers studied the PEC etching kinetics of In x Ga 1‐x N . This method represents an accelerated etching process compared to common dark etching.…”

“…Hwang and co-workers studied the PEC etching kinetics of In x Ga 1-x N. [64] This method represents an accelerated etching process compared to common dark etching. In these experiments, a dependency of the etching rate on solution agitation was observed.…”