Micro LED Light-Transmissive Layer Extension
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Solution Overview
Problem
Micro LEDs face reduced optical efficiency due to a light-transmissive layer that is retracted from the edge of the epitaxial structure, resulting in untransmitted light, as the current lithography process limits the area of the light-transmissive layer to be smaller than the top surface of the epitaxial structure.
Innovation Solution
A micro device design where the light-transmissive layer covers the top surface of the epitaxial structure and extends over the peripheral surface exposed by the insulating layer, ensuring the area of the light-transmissive layer is greater than the top surface area, with specific thickness and material considerations to enhance optical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the light-transmissive layer is formed by lithography process, then the manufacturing process is simplified, but the area of the light-transmissive layer becomes smaller than the top surface area of the epitaxial structure, reducing optical efficiency
Solution Approach 1:
The light-transmissive layer is extended from merely covering the top surface to also covering the peripheral surface of the epitaxial structure. This dimensional extension allows the layer to reach edges and corners that lithography can accommodate, increasing the effective light transmission area without requiring higher lithography precision.
Solution Approach 2:
The light-transmissive layer is designed to nest over the peripheral surface in a stepped configuration, with different thickness regions (first thickness on top surface, second thickness on peripheral surface). This nested structure allows the layer to conform to the epitaxial structure's geometry while maintaining manufacturing feasibility.
2Productivity
If the light-transmissive layer area is increased to cover the entire top surface, then optical efficiency improves, but the lithography process margin becomes too small
Solution Approach 1:
The light-transmissive layer is segmented into different thickness regions: a first thickness on the top surface and a second thickness on the peripheral surface. This segmentation allows each region to be optimized independently, with the peripheral region extending closer to edges to improve optical efficiency while the top surface region maintains manufacturing tolerance.
Solution Approach 2:
Different regions of the light-transmissive layer are given different thicknesses to serve different functions. The first thickness region on the top surface provides uniform light transmission, while the second thickness region on the peripheral surface extends to the edges to capture and transmit light from the periphery, with each region's thickness optimized for its specific location.
3Productivity
If the light-transmissive layer is extended over the peripheral surface, then more light is transmitted outward, but the structural complexity increases
Solution Approach 1:
The light-transmissive layer serves multiple functions: it provides optical transmission on the top surface, extends to protect and transmit light from the peripheral surface, and forms a integrated structure with the insulating layer. This multi-functionality is achieved through a single continuous layer design rather than separate components.
Solution Approach 2:
The light-transmissive layer and insulating layer are merged into a single continuous structure, with the light-transmissive layer extending beyond the insulating layer's coverage. This merging simplifies the overall device structure while achieving both electrical insulation and enhanced optical transmission functions.
Data Source
AI summary
A micro device includes an epitaxial structure, an insulating layer, and a light-transmissive layer. The epitaxial structure has a top surface and a bottom surface opposite to each other and a peripheral surface connected to the top surface and the bottom surface. The insulating layer covers the peripheral surface and the bottom surface of the epitaxial structure and exposes a portion of the peripheral surface. The light-transmissive layer covers the top surface of the epitaxial structure and is extended over at least a portion of the portion of the peripheral surface.