Ohmic Contacts for GaN Substrates via Anisotropic Etching
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Solution Overview
Problem
Conventional methods for manufacturing ohmic contacts for gallium nitride (GaN) light emitting diodes (LEDs) face challenges in achieving high electrical efficiency and reflectivity, with silver being unsuitable for n-GaN contacts and existing methods leading to high contact resistance and reliability issues.
Innovation Solution
A method involving a gallium and nitrogen containing substrate with a polished backside surface subjected to anisotropic etching to form pyramid-like structures, followed by plasma and acid treatments, and deposition of aluminum or titanium bearing species to create low-resistance ohmic contacts with high reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods are used to manufacture ohmic contacts for GaN LEDs, then the manufacturing process is simple, but the contact resistance is high and reliability is poor
Solution Approach 1:
The patent applies preliminary action by performing surface preparation steps (polishing, anisotropic etching to form pyramid structures, plasma treatment, and chemical treatment) before depositing the contact material. These preliminary treatments modify the GaN surface properties in advance to ensure low contact resistance and high reliability, rather than attempting to achieve good contact properties through the contact material deposition alone.
Solution Approach 2:
The patent changes the physical and chemical parameters of the GaN surface through multiple treatment steps: polishing changes surface roughness, anisotropic etching changes surface morphology to create pyramid structures, plasma treatment changes surface chemistry and cleanliness, and chemical treatment further modifies surface properties. These parameter changes enable the formation of reliable ohmic contacts with low contact resistance.
2Loss of energy
If silver is used for n-GaN contacts, then the reflectivity is high, but the electrical efficiency is poor due to high contact resistance
Solution Approach 1:
The patent changes the electrical parameters of the contact interface by treating the GaN surface to reduce contact resistance. The combination of mechanical polishing, anisotropic etching, plasma treatment, and chemical treatment modifies the surface properties to enable low-resistance electrical contact, thereby reducing energy loss while maintaining or improving reflectivity through the contact material deposition.
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 results in ohmic contacts with reduced contact resistance and improved reflectivity, enhancing the electrical efficiency and reliability of GaN LEDs, while avoiding the limitations of previous techniques.
Implementation Method 1
subjecting the backside surface to an anisotropic etching process exposing various crystal planes to form a plurality of pyramid-like structures distributed spatially in a non-periodic manner on the backside surface
Implementation Method 2
treating the backside surface, comprised of a plurality of pyramid-like structures, to a plasma species
Data Source
AI summary
Techniques for manufacturing optical devices are disclosed. More particularly, light emitting diodes and in particular to ohmic contacts for light emitting diodes are disclosed.