Micro-LED Light Extraction via Curved Semiconductor Layer
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Solution Overview
Problem
Micro-light-emitting diodes have insufficient brightness due to their small light-emitting area, leading to inadequate light extraction efficiency.
Innovation Solution
The micro-light-emitting diode device features a second semiconductor layer with varying thicknesses, where the center thickness is greater than the edge thickness, creating a protruding center in the light-exiting surface, which reduces the probability of light being totally reflected inside the device and increases light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the light-emitting area is reduced to create micro-LEDs, then the device size is reduced, but the light extraction efficiency becomes insufficient
Solution Approach 1:
The second semiconductor layer is designed with non-uniform thickness, where the thickness at the light-exiting surface varies across different regions. Specifically, the thickness is greater at the center and smaller at the edges, creating local variations in optical path length that improve light extraction efficiency without increasing the overall device footprint
Solution Approach 2:
The light-exiting surface of the second semiconductor layer is formed with a curved or domed profile rather than a flat surface. This curvature creates varying thickness across the surface, which helps to reduce total internal reflection and improve light extraction efficiency while maintaining the micro-LED's small size
2Ease of manufacture
If the second semiconductor layer has uniform thickness, then the manufacturing is simpler, but the light extraction efficiency is insufficient
Solution Approach 1:
The second semiconductor layer transitions from uniform thickness to non-uniform thickness with the light-exiting surface having varying thickness across different regions. This local variation in thickness is designed to optimize light extraction by creating different optical path lengths in different areas, improving overall light extraction efficiency
Solution Approach 2:
The thickness parameter of the second semiconductor layer is deliberately varied across the light-exiting surface. By changing the thickness parameter from uniform to non-uniform distribution, the optical properties are optimized to reduce total internal reflection and enhance light extraction efficiency
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 design enhances light extraction efficiency and overall brightness of the micro-light-emitting diode device without the need for additional lenses, providing a focusing effect and reducing light trapping.
Implementation Method 1
reduces the probability of light being totally reflected inside the device
Implementation Method 2
provide a focusing effect for the light by the light-exiting surface
Data Source
AI summary
A micro-light-emitting diode device includes a first semiconductor layer, an active layer, and a second semiconductor layer. The first semiconductor layer has a first bottom surface. The active layer is disposed on the first semiconductor layer. The second semiconductor layer is disposed on the active layer. The second semiconductor layer and the active layer have an interface. A surface of the second semiconductor layer opposite to the active layer is a light-exiting surface of the micro-light-emitting diode device. A distance between the light-exiting surface and the interface decreases from a central axis of the second semiconductor layer to an edge of the second semiconductor layer, so as to provide a focusing effect for the light by the light-exiting surface.