Ultrafast physical sputtering of GaN by electrosprayed nanodroplet beams

• Nanodroplet etching of GaN demonstrates sputtering rates as high as 1745 nm/min.
• This physical sputtering rate is superior to that of plasma etching process.
• Nanodroplet sputtering is a molecular process, it does not follow continuum laws.

GaN is a wide-bandgap semiconductor used for light-emitting diodes, laser diodes, UV detectors, power electronics, and microelectromechanic devices. Etching is a key step in the fabrication of these devices, but it is difficult and slow due to the chemical stability and the strong interatomic bonds that make GaN a superior material over the industry-standard Si. Reactive ion etching by high density plasmas, with a maximum etching rate of 1300 nm/min, is the process of choice for GaN. This letter presents a novel and faster etching method based on the bombardment by electrosprayed nanodroplets. The energetic impact of these projectiles ejects atoms by physical sputtering and, under the non-optimized beams conditions employed in our research, demonstrates etching rates on GaN as high as 1745 nm/min and sputtering yields in excess of 25 atoms per projectile’s molecule.

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