Hexagonal LED Sidewall Structure for Brightness and Yield
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face challenges in achieving improved production yield and brightness, particularly in smaller form factors, due to limitations in cutting technology and lattice mismatch issues that affect epitaxy quality and light extraction efficiency.
Innovation Solution
A light-emitting device with a hexagonal crystal structure substrate featuring tilted side surfaces and a folded structure, where the side surfaces are designed to form acute angles with the m-plane, and a pitch between modified regions is maintained above 5 μm, enhancing light extraction and reducing dislocation through patterned structures and laser irradiation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional cutting technology is used for smaller LEDs, then device size is reduced, but production yield and epitaxy quality deteriorate due to lattice mismatch issues
Solution Approach 1:
The substrate is divided into multiple domains with different crystal orientations by introducing domain boundaries. This segmentation allows different regions to accommodate lattice mismatch differently, reducing dislocation propagation and improving epitaxy quality in smaller LEDs while maintaining high production yield
Solution Approach 2:
Different regions of the substrate are given different crystal orientations and properties. Specifically, the substrate includes first domains with a first crystal orientation and second domains with a second crystal orientation, allowing local optimization of lattice matching for each region to improve overall device reliability
2Ease of manufacture
If conventional flat substrate structure is used, then manufacturing is simple, but light extraction efficiency is limited
Solution Approach 1:
The substrate structure transitions from a flat two-dimensional surface to a three-dimensional folded structure with multiple domains and boundaries. This dimensional change creates additional light extraction pathways and reduces total internal reflection, significantly improving light extraction efficiency while maintaining manufacturability through controlled growth processes
3Volume of moving object
If smaller LED size is achieved, then device volume is reduced, but brightness and luminous intensity deteriorate
Solution Approach 1:
The crystal orientation parameters of the substrate are changed to include multiple domains with different orientations. This parameter change optimizes light extraction in multiple directions, compensating for the reduced device volume and maintaining or even enhancing brightness through improved luminous intensity distribution
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 solution improves the brightness and production yield of LEDs by optimizing light extraction and reducing dislocation, resulting in enhanced luminous intensity distribution and improved manufacturing efficiency.
Implementation Method 1
the first side surface is tilted away from a m-plane of the hexagonal crystal structure, and an acute angle is formed between the first side surface and the m-plane
Implementation Method 2
the first side surface comprises a first modified stripe, and the first modified stripe comprises a plurality of first modified regions
Data Source
AI summary
A light-emitting device includes a substrate comprising an upper surface, a plurality of side surfaces, and a semiconductor stack located on the upper surface. The substrate includes a hexagonal crystal structure. The plurality of side surfaces includes a first side surface. The first side surface is tilted away from a m-plane of the hexagonal crystal structure, and an acute angle is formed between the first side surface and the m-plane. The first side surface includes a first modified stripe, and the first modified stripe includes a plurality of first modified regions. A pitch is between the adjacent first modified regions, and the pitch is not less than 5 μm. The first side surface comprises a folded structure.