GaN Substrate Backside Pyramids for Low Resistance LED Contacts
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Solution Overview
Problem
Conventional methods for manufacturing high-efficiency light emitting diodes (LEDs) face challenges in optimizing internal and extraction efficiencies, particularly due to internal absorption and the complexity of forming ohmic contacts on gallium nitride (GaN) substrates, which affect luminance per watt.
Innovation Solution
A method involving a gallium and nitrogen containing substrate with a backside surface treated to form pyramid-like structures through polishing and anisotropic etching, followed by plasma and acid treatments, to create a contact material with aluminum or titanium species, enhancing ohmic contact formation and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polishing and contact formation methods are used on GaN substrates, then manufacturing process is simple, but contact resistance is high and ohmic contact formation is difficult
Solution Approach 1:
The patent applies preliminary surface treatment actions including polishing to create specific roughness (0.3-200 nm), anisotropic etching to form pyramid-like structures, and plasma treatment before contact material deposition. These preliminary actions modify the GaN substrate surface to enhance subsequent ohmic contact formation and reduce contact resistance.
Solution Approach 2:
The patent creates localized pyramid-like structures with specific geometries (height 20-1000 nm) distributed non-periodically on the substrate surface. These localized structural modifications provide optimal contact properties in specific regions while maintaining overall substrate integrity.
2Use of energy by moving object
If internal efficiency is improved, then luminance per watt increases, but extraction efficiency optimization is more impactful and simpler
Solution Approach 1:
Instead of focusing on improving internal quantum efficiency through complex active region modifications, the patent inverts the approach by optimizing extraction efficiency through backside surface treatment. This alternative pathway achieves luminance per watt improvement through simpler manufacturing processes.
Solution Approach 2:
The patent shifts the optimization focus from the front side active region (traditional approach) to the backside surface of the substrate. This dimensional shift allows extraction efficiency improvement without complicating the active region structure or material composition.
3Illumination intensity
If pyramid-like structures are formed through anisotropic etching, then light extraction efficiency improves, but manufacturing process complexity increases
Solution Approach 1:
The patent replaces complex mechanical or lithographic patterning methods with chemical anisotropic etching to form pyramid-like structures. This substitution simplifies the manufacturing process by utilizing self-organizing chemical reactions during plasma treatment to create the desired microstructures.
Solution Approach 2:
The anisotropic etching process exploits the natural crystallographic properties of GaN to self-organize into pyramid-like structures during plasma treatment. The process uses the substrate's own crystal structure to guide the formation of optimal light extraction features without requiring external patterning templates.
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 improves the luminance efficiency of LEDs by forming low-resistance ohmic contacts with high reflectivity, facilitating better light extraction and reducing operating costs and greenhouse gas emissions.
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
A method for fabricating LED devices. The method includes providing a gallium and nitrogen containing substrate member (e.g., GaN) comprising a backside surface and a front side surface. The method includes subjecting the backside surface to a polishing process, causing a backside surface to be characterized by a surface roughness, 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, treating the backside surface comprising the plurality of pyramid-like structures, to a plasma species, and subjecting the backside surface to a surface treatment. The method further includes forming a contact material comprising an aluminum bearing species or a titanium bearing species overlying the surface-treated backside to form a plurality of LED devices with the contact material.