GaN LED Light Extraction via Laser-Ablated Undulated Sidewalls
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Solution Overview
Problem
Existing techniques for manufacturing Group III-nitride volumetric LED chips fail to achieve high-performance light extraction due to limitations in surface and sidewall roughening, particularly with traditional cleaving methods not effectively patterning or roughening the surfaces of GaN-based LEDs.
Innovation Solution
The implementation of undulated slanted sidewalls and surface roughening techniques through laser ablation and etching processes to enhance light extraction, including 1-dimensional and 2-dimensional sidewall roughening, and varying surface roughness to break quasi-guided light trajectories and improve external quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional cleaving methods are used to manufacture Group III-nitride volumetric LED chips, then the manufacturing process is simple, but light extraction efficiency is low
Solution Approach 1:
The patent applies parameter changes by modifying the surface and sidewall properties of the LED chip through laser ablation and chemical etching. The surface roughness is controlled at 80-10,000 nm and sidewall roughness at 80-5,000 nm, transforming the optical properties to enhance light extraction from the semiconductor/air interface
Solution Approach 2:
The patent introduces dimensional changes by creating undulated slanted sidewalls with specific roughness characteristics. This adds surface complexity in multiple dimensions, transforming light trajectories through randomized paths and improving extraction from both top and lateral surfaces
2Reliability
If surface and sidewall roughening is applied to improve light extraction, then light extraction efficiency increases, but manufacturing complexity increases
Solution Approach 1:
The patent segments the surface treatment process into distinct stages: laser ablation creates initial roughness, followed by chemical etching that develops the undulated sidewall structure. This segmentation allows control over different aspects of surface morphology independently
Solution Approach 2:
The patent replaces traditional mechanical cleaving methods with laser ablation technology. This substitution enables precise control over surface roughness parameters and creates the desired undulated sidewall structure that mechanical methods cannot achieve
3Reliability
If undulated slanted sidewalls are created to break quasi-guided light trajectories, then light extraction efficiency improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by using laser ablation to create an initial roughened surface and undulated sidewall structure before chemical etching. This pre-structuring guides the subsequent etching process to develop the final roughness pattern with controlled parameters
Solution Approach 2:
The patent uses chemical etchants as intermediaries to transform the laser-ablated surface into the final undulated sidewall structure. The chemical etching process mediates between the initial laser pattern and the desired final surface morphology, allowing controlled development of roughness features
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
This approach significantly boosts light extraction efficiency, achieving up to ~82% extraction efficiency by randomizing light trajectories and increasing the escape of emitted light from the semiconductor/air or semiconductor/encapsulant interface, thereby enhancing the overall performance of Group III-nitride LED chips.
Implementation Method 1
laser ablation and etching processes to enhance light extraction
Implementation Method 2
break these quasi-guided trajectories... by shaping and texturing of the sidewall facets... randomizing light trajectories
Data Source
AI summary
A method of fabricating LEDs from a wafer comprising a substrate and epitaxial layers and having a substrate side and a epitaxial side, said method comprising: (a) applying a laser beam across at least one of said substrate side or said epitaxial side of said wafer to define at least one laser-scribed recess having a laser-machined surface; and (b) singulating said wafer along said laser-scribed recess to form singulated LEDs, said singulated LEDs having a top surface, a bottom surface, and a plurality of sidewalls, at least one of said sidewalls comprising at least a first portion comprising at least a portion of said laser-machined surface.