Abstract
The formation of gallium nitride (GaN) semi-polar and non-polar nanostructures is of importance for improving light extraction/absorption of optoelectronic devices, creating optical resonant cavities or reducing the defect density. However, very limited studies of nanotexturing via dry etching have been performed, in comparison to wet etching. In this paper, we investigate the formation and morphology of semi-polar () and non-polar () GaN nanorods using inductively coupled plasma (ICP) etching. The impact of gas chemistry, pressure, temperature, radio-frequency (RF) and ICP power and time are explored. A dominant chemical component is found to have a significant impact on the morphology, being impacted by the polarity of the planes. In contrast, increasing the physical component enables the impact of crystal orientation to be minimized to achieve a circular nanorod profile with inclined sidewalls. These conditions were obtained for a small percentage of chlorine (Cl2) within the Cl2 + argon (Ar) plasma combined with a low pressure. Damage to the crystal was reduced by lowering the direct current (DC) bias through a reduction of the RF power and an increase of the ICP power.
Highlights
Semi-polar and non-polar gallium nitride (GaN) crystal orientations have received considerable attention owing to their many potential advantages over the polar orientation of c-plane GaN
Among these results, and many more showing reasonable performances, all were obtained from freestanding semi-/non-polar GaN substrates [1,2], while only a few mentioned the use of surface patterning to increase light extraction [4,5]
We investigate the impact of inductively coupled plasma (ICP) etching conditions on the morphology, the etch rate and dimensions of GaN nanorods for various plane orientations
Summary
Semi-polar and non-polar gallium nitride (GaN) crystal orientations have received considerable attention owing to their many potential advantages over the polar orientation of c-plane GaN. Some remarkable external quantum efficiency (EQE) values have been reported across the purple [3], the blue [4,5,6] and the green wavelength ranges [7,8] Among these results, and many more showing reasonable performances, all were obtained from freestanding semi-/non-polar GaN substrates [1,2], while only a few mentioned the use of surface patterning to increase light extraction [4,5]. The fabrication of highly organized and uniform textured surfaces with tuneable profile and etch depth is of high interest to reduce the defect density and improve light extraction It could be beneficial for the creation of resonant nano-microcavites. We deduce that a small percentage of chlorine (Cl2) into the Cl2 + Ar plasma combined with a low pressure enables achieving a circular nanorod profile with inclined sidewalls independently of the crystal orientation
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