Optimization of inductively coupled plasma deep etching of GaN and etching damage analysis

Inductively coupled plasma (ICP) etching of GaN with an etching depth up to 4 μm is systemically studied by varying ICP power, RF power and chamber pressure, respectively, which results in etch rates ranging from ∼370 nm/min to 900 nm/min. The surface morphology and damages of the etched surface are characterized by optical microscope, scanning electron microscope, atomic force microscopy, cathodoluminescence mapping and photoluminescence (PL) spectroscopy. Sub-micrometer-scale hexagonal pits and pillars originating from part of the structural defects within the original GaN layer are observed on the etched surface. The density of these surface features varies with etching conditions. Considerable reduction of PL band-edge emission from the etched GaN surface indicates that high-density non-radiative recombination centers are created by ICP etching. The density of these non-radiative recombination centers is found largely dependent on the degree of physical bombardments, which is a strong function of the RF power applied. Finally, a low-surface-damage etch recipe with high ICP power, low RF power, high chamber pressure is suggested.

Research highlights▶ Inductively coupled plasma (ICP) deep etching of GaN is systemically studied by varying ICP power, RF power and chamber pressure, respectively. ▶ The quality of the etched GaN surface is found to be largely dependent on the RF power applied while the ICP power and chamber pressure play a relatively minor role. ▶ Sub-micrometer-scale hexagonal pits and pillars originating from part of the structural defects within the original GaN layer are observed on the etched surface. ▶ Considerable reduction of PL band-edge emission from the etched GaN surface indicates that high-density non-radiative recombination centers are created by ICP etching. ▶ A low-surface-damage etch recipe with high ICP power, low RF power, high chamber pressure is suggested.