Triangular GaN LED Chip Geometry for Light Extraction
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Solution Overview
Problem
Conventional LED fabrication processes face challenges in achieving high-intensity, high-efficiency GaN-based green LEDs and are costly to produce on a wide scale, with conventional light bulbs dissipating over 90% of energy as thermal energy and frequently failing due to thermal expansion.
Innovation Solution
The method involves scribing and breaking bulk c-plane GaN wafers along non-orthogonal axes to create triangular or diamond-shaped chip geometries, leveraging the in-plane 6-fold rotational symmetry of c-plane GaN wafers, which enhances light extraction efficiency by reducing total internal reflection and increasing the probability of in-plane emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional wafer scribing and breaking procedure is used to produce square or rectangular LED chips, then the fabrication process is simple and straightforward, but the light extraction efficiency is reduced due to total internal reflection at the sidewalls
Solution Approach 1:
The patent applies asymmetry by transitioning from conventional square or rectangular chip geometries to triangular chip geometries. The triangular shape with specific crystallographic orientations (m-plane or a-plane sidewalls) asymmetrically modifies the light extraction paths, reducing total internal reflection and enhancing light emission efficiency compared to the symmetric square geometry.
Solution Approach 2:
The patent changes the geometric parameter of the chip from square/rectangular to triangular shape, and modifies the crystallographic orientation parameters of the sidewalls. This parameter change in geometry and orientation directly impacts the optical properties, improving light extraction efficiency by altering the total internal reflection characteristics at the chip boundaries.
2Manufacturing precision
If conventional lapping and polishing steps are used in LED fabrication, then the manufacturing process is thorough and precise, but the production cost increases significantly
Solution Approach 1:
The patent extracts or removes the expensive lapping and polishing steps from the conventional fabrication process. By designing the wafer singulation process to directly produce the desired triangular chip geometry through scribing and breaking alone, the patent eliminates the need for subsequent costly surface finishing operations while maintaining adequate manufacturing precision.
Solution Approach 2:
The patent employs a less expensive scribing and breaking process instead of costly lapping and polishing. The scribe lines created during the breaking process serve as sufficient surface definitions for the triangular chips, making additional precision surface treatment unnecessary and reducing overall production costs.
3Productivity
If GaN-based LEDs are produced on a wide scale using conventional methods, then production volume increases, but the cost remains high and efficiency for green LEDs is particularly problematic
Solution Approach 1:
The patent segments the wafer into multiple triangular chips through scribing along three axes at 60-degree angles, creating a pattern that efficiently utilizes the entire wafer area. This segmentation approach, combined with the triangular geometry, allows for higher chip density and improved productivity while reducing waste and manufacturing costs.
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 results in improved light extraction efficiency and reduced production costs by eliminating the need for expensive lapping and polishing steps, with triangular-shaped chips showing increased light extraction efficiency compared to conventional square or rectangular chips.
Implementation Method 1
enhances light extraction efficiency by reducing total internal reflection
Data Source
AI summary
A gallium and nitrogen containing optical device has a base region and no more than three major planar side regions configured in a triangular arrangement provided from the base region.