Photoelectrochemical Etching for GaN Trench Damage Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Regrown junctions in semiconductor devices exhibit higher reverse leakage currents due to etch-induced damage and impurity incorporation, particularly in etched-trench geometry devices, which degrades the electrical performance and increases defect density.
Innovation Solution
A photoelectrochemical etching process is used to remove dry-etch damage from Al/In/GaN films by immersing the substrate in an electrolyte solution and illuminating it with above bandgap light, generating electron-hole pairs to selectively etch and mitigate surface defects, allowing for high-quality regrowth of p-n junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If dry etching is used to form trenches in GaN substrates, then device architecture complexity is improved, but surface damage and defect density increase
Solution Approach 1:
The patent replaces the mechanical/physical dry etching process with a photoelectrochemical etching process that uses light and chemical reactions to remove material. This substitution eliminates ion bombardment and mechanical stress that cause surface damage, while still achieving the required trench formation for device architecture.
Solution Approach 2:
The patent changes the etching mechanism from physical/chemical plasma-based dry etching to photoelectrochemical etching by introducing light illumination and electrolyte solutions. This parameter change transforms the etching process to one that selectively removes damaged material without introducing additional surface defects.
2Device complexity
If regrown junctions are formed in etched trenches, then vertical device architecture is achieved, but reverse leakage current increases
Solution Approach 1:
The patent converts the harmful effect of dry etching (surface damage) into a beneficial process by using photoelectrochemical etching to selectively remove only the damaged regions. The light-induced electrochemical reaction targets and removes etch-induced defects while preserving the underlying crystal structure, thereby reducing reverse leakage current in regrown junctions.
Solution Approach 2:
The patent introduces an intermediary photoelectrochemical treatment step between dry etching and regrowth. This intermediary process uses light and electrolyte as mediators to clean the trench surfaces of damaged material and impurities, creating a cleaner interface for subsequent epitaxial regrowth and reducing leakage paths.
3Productivity
If dry etching is performed to create trenches, then device fabrication progress is improved, but impurity incorporation increases
Solution Approach 1:
The patent replaces the mechanical sputtering and ion bombardment of dry etching with a photoelectrochemical dissolution process. This substitution prevents mechanical disruption of the crystal lattice that would incorporate impurities, while maintaining efficient trench formation for device fabrication.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively reduces reverse leakage currents and improves the surface smoothness of GaN surfaces, enabling the formation of high-quality etched-and-regrown p-n junctions with reduced defect density, as evidenced by enhanced photoluminescence ratios indicating improved material quality.
Implementation Method 1
illuminated with above bandgap light having a wavelength that generates electron-hole pairs in the n-type Al/In/GaN semiconductor material
Implementation Method 2
photoelectrochemically etching the surface to remove at least a portion of the dry-etch damage
Data Source
AI summary
A method comprises providing a substrate comprising an n-type Al/In/GaN semiconductor material. A surface of the substrate is dry-etched to form a trench therein and cause dry-etch damage to remain on the surface. The surface of the substrate is immersed in an electrolyte solution and illuminated with above bandgap light having a wavelength that generates electron-hole pairs in the n-type Al/In/GaN semiconductor material, thereby photoelectrochemically etching the surface to remove at least a portion of the dry-etch damage.