Deep and alignment free patterned etching of GaN surface using an atomic force microscope.

Area of Science:

• Materials Science
• Nanotechnology
• Surface Engineering

Background:

• Gallium Nitride (GaN) is a critical material for electronic and optoelectronic devices.
• Precise and scalable surface patterning techniques are essential for advanced GaN device fabrication.
• Existing methods often require complex alignment and multiple processing steps.

Purpose of the Study:

• To develop a novel, alignment-free method for deep patterned etching on GaN.
• To demonstrate the feasibility of using atomic force microscopy (AFM) for localized oxidation and subsequent chemical etching.
• To investigate the characteristics of the AFM-grown oxide and its impact on etching depth and porosity.

Main Methods:

• Localized oxidation of GaN using AFM with a positive sample bias, 80% humidity, and UV light.
• In-situ chemical etching of the grown oxide ridges using hydrochloric acid (HCl).
• Development of a dripping strategy for efficient and repeatable etching without substrate removal from the AFM platform.

Main Results:

• Achieved deep (up to 800 nm) and alignment-free patterned etching on GaN surfaces.
• Demonstrated multiple oxidation/etching cycles on the same GaN area.
• Characterized the AFM-grown oxide, revealing a porous structure (estimated 86% porosity) at a cantilever speed of 300 nm/s, with potential for porosity reduction.

Conclusions:

• The combined AFM local oxidation and in-situ chemical etching offers a versatile and efficient approach for deep, alignment-free GaN patterning.
• The developed dripping strategy facilitates multi-step processing directly on the AFM platform.
• Understanding and controlling oxide porosity is key to optimizing etching depth and surface morphology for GaN nanotechnology applications.