Selective chemical etch of gallium nitride by phosphoric acid

The authors report on the direct comparison of the chemical etch characteristics on both Ga- and N-face gallium nitride (GaN) by phosphoric acid. First, Ga-face GaN was grown next to N-face GaN by a polarity inversion method in a metal-organic chemical vapor deposition reactor. Micro-photoluminescence, atomic force microscopy, scanning electron microscopy, and micro-Raman spectroscopy were used to analyze the etch characteristics of Ga- and N-face GaN before and after a H ₃PO ₄-based chemical etch. Ga-face was chemically stable in a phosphoric acid solution. However, the chemical etch continued proceeding on the N-face GaN due to the weak repulsive force to OH ^- ions. Dodecagonal nano-pyramids which dramatically enhanced the photoluminescence intensity were observed on N-face GaN after a H ₃PO ₄-based chemical etch.