Efficient wet etching of GaN (0001) substrate with subsurface damage layer.

Area of Science:

• Materials Science
• Surface Chemistry
• Semiconductor Processing

Background:

• Photoenhanced chemical (PEC) etching offers rapid processing for n-GaN (0001) surfaces.
• Surface oxidation, enhanced by photo-generated holes, facilitates oxide dissolution in solutions.
• Mechanical polishing with sub-micrometer diamond slurry creates crystallographically damaged layers on n-GaN.

Purpose of the Study:

• To investigate the effectiveness of bias-assisted PEC etching for removing damaged n-GaN (0001) surfaces.
• To understand the role of applied bias in overcoming recombination losses of photogenerated carriers.
• To achieve high material removal rates on mechanically polished n-GaN.

Main Methods:

• Utilizing bias-assisted photoenhanced chemical (PEC) etching.
• Employing a potassium hydroxide (KOH) solution as the etchant.
• Applying a positive bias to the n-GaN (0001) wafer during etching.

Main Results:

• Without applied bias, PEC etching rates were low due to rapid recombination of photogenerated holes at crystallographic defects.
• Applying a positive bias effectively separated photogenerated holes and electrons at the band-bended surface.
• This bias-induced carrier separation significantly enhanced surface oxidation and material removal.
• A high removal rate was achieved even on the mechanically damaged n-GaN surface.

Conclusions:

• Bias-assisted PEC etching is a highly effective method for rapidly processing damaged n-GaN (0001) surfaces.
• The applied positive bias is crucial for overcoming carrier recombination and enhancing the oxidation process.
• This technique enables efficient removal of crystallographically damaged layers, improving n-GaN surface quality.