Chemical etching behaviors of semipolar (112̄2) and nonpolar (112̄0) gallium nitride films

Abstract

Wet chemical etching using hot KOH and H3PO4 solutions was performed on semipolar (11̄22) and nonpolar (11̄20) GaN films grown on sapphire substrates. An alternating KOH/H3PO4/KOH etch process was developed to control the orientation of the facets on the thin-film surface. The initial etch step in KOH produced c- and m-plane facets on the surface of both semipolar (11̄22) and nonpolar (11̄20) GaN thin-films. A second etch step in H3PO4 solution additionally exposed a (̄1̄12̄2) plane, which is chemically stable in H3PO4 solution. By repeating the chemical etch with KOH solution, the m-plane facets as seen in the original KOH etch step were recovered. The etching methods developed in our work can be used to control the surface morphologies of nonpolar and semipolar GaN-based optoelectronic devices such as light-emitting diodes and solar cells.

Semipolar (112̅2) AlGaN-Based Solar-Blind Ultraviolet Photodetectors with Fast Response

“…KOH wet etching has the advantages of being simple and convenient, which could be used to improve light extraction efficiency of LEDs and remove the dry etching damages of GaN. , In 2003, the leakage current mechanism of AlGaN Schottky interface based on the thin surface barrier model had been studied, in which the effect of surface defects was considered . In order to solve the common problem of low PDCR in III-nitride-based PDs, we used KOH wet etching to reduce the dark current and improve the PDCR.…”

High-performance light-emitting diodes using hierarchical m-plane GaN nano-prism light extractors

“…As a second difficulty, preventing the occurrence of unwanted defects, like etch pits, even at a lower temperature is also difficult. 23,24 Jung et al, 23 reporting the KOH chemical etching of GaN films on a hotplate at 100 1C for 20 min, showed triangular etch pits on the m-plane surface. Similar behaviours was also reported by Rass et al 24 Once the pits are formed on the etched device, they give rise to an increased leakage current and consequently a poor device-reliability behaviour.…”

Modification of the Surface Properties of AlxGa1–xN Substrates with Gradient Aluminum Composition Using Wet Chemical Treatments

“…17,25,31,32 Preferential etching by H 3 PO 4 forms etch pits with hexagonal morphology where dislocations are located at the surface of polar GaN films. 17,33,34 We used H 3 PO 4 to modify the surface nanostructure and chemistry of the Al x Ga 1– x N film in the fourth set of samples to cause a change in surface properties. We added (3-bromopropyl)phosphonic acid (C 3 H 8 BrO 3 P) to H 3 PO 4 for the treatment of the fifth set of samples to functionalize the surface with a phosphonic acid to prevent oxide formation, which we have previously reported on GaN.…”

“…After H 2 O 2 passivation, the third set of the samples was capped with a hydrocarbon using 4-chlorobutyric acid (C 4 H 7 ClO 2 ) to inhibit oxide formation after chemical treatment. It is well documented in the literature that the etch rate of H 3 PO 4 at surface pits resulting from dislocations in III-nitrides is faster than defect-free areas by the removal of Ga atoms at the surface through oxide formation. ,,, Preferential etching by H 3 PO 4 forms etch pits with hexagonal morphology where dislocations are located at the surface of polar GaN films. ,, We used H 3 PO 4 to modify the surface nanostructure and chemistry of the Al x Ga 1– x N film in the fourth set of samples to cause a change in surface properties. We added (3-bromopropyl)­phosphonic acid (C 3 H 8 BrO 3 P) to H 3 PO 4 for the treatment of the fifth set of samples to functionalize the surface with a phosphonic acid to prevent oxide formation, which we have previously reported on GaN …”