Patterned LED Substrate Etching for Uniform Light Extraction
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Solution Overview
Problem
The lattice mismatch between sapphire and GaN in optoelectronic devices results in high defect density and low light-extraction efficiency, which is not adequately addressed by existing patterned sapphire substrates.
Innovation Solution
A light-emitting device with a patterned substrate featuring protrusions and recesses, where the epitaxial unit is selectively etched to create a height difference of no greater than 1 μm between uncovered and covered areas, enhancing lattice mismatch alleviation and improving current spreading and light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the epitaxial layer is completely removed in uncovered areas, then luminance uniformity is improved, but the manufacturing precision requirement increases
Solution Approach 1:
The substrate is pre-patterned with protrusions of different heights before epitaxial growth, establishing a preliminary structural framework. This preliminary action guides the subsequent epitaxial layer formation and ensures complete removal in uncovered areas while maintaining controlled height differences, reducing final manufacturing precision requirements.
Solution Approach 2:
The invention changes the physical parameters of the substrate surface by creating protrusions with specific height differences (no greater than 1 μm). This parameter change enables complete epitaxial layer removal in uncovered areas to improve luminance uniformity, while the controlled height difference maintains manufacturing feasibility.
2Reliability
If the height difference between uncovered and covered areas is controlled to no greater than 1 μm, then current spreading is improved, but the device complexity increases
Solution Approach 1:
The invention transitions from a two-dimensional flat substrate to a three-dimensional structured substrate with vertical height variations. This dimensional change enables improved current spreading through the height difference (no greater than 1 μm) while maintaining a relatively simple overall structure that does not excessively increase device complexity.
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 reduces defect density and enhances light-extraction efficiency by ensuring complete removal of the epitaxial layer in uncovered areas, improving luminance uniformity and reliability of the light-emitting device.
Implementation Method 1
a lattice mismatch between sapphire and GaN is about 15%, which may result in a high defect density in an epitaxial layer of the optoelectronic device
Implementation Method 2
The epitaxial unit includes a first semiconductor layer, an active layer, and a second semiconductor layer that are sequentially disposed on the first surface of the substrate in such order
Implementation Method 3
A light-emitting diode (LED) that includes a light-emitting material may produce light through re-combinations of electrons and holes
Data Source
AI summary
A light-emitting device includes a substrate and an epitaxial unit. The substrate has a first and a second surface. The substrate is formed on the first surface with a plurality of protrusions. The epitaxial unit includes a first semiconductor layer, an active layer, and a second semiconductor layer that are sequentially disposed on the first surface of the substrate. The first surface of the substrate has a first area that is not covered by the epitaxial unit, and a second area this is covered by the epitaxial unit. A height difference (h2) between the first area and the second area is no greater than 1 μm. A display apparatus and a lighting apparatus are also disclosed.