Micro-LED Micro-Lens Structure for Small-Cone Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Micro-LEDs with reduced physical dimensions face challenges in improving their low external quantum efficiency, internal quantum efficiency, and light extraction efficiency, particularly in collecting light within a small emission cone for display applications.
Innovation Solution
The design includes a micro-LED with a semiconductor mesa structure and a micro-lens on a spacer layer, where the spacer layer's thickness is optimized to position the focal point at the front surface of the mesa, and the micro-lens is larger than the mesa, enhancing light collimation and extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If micro-LED physical dimensions are reduced to achieve high packing density and resolution, then device size and resolution are improved, but light extraction efficiency and external quantum efficiency deteriorate
Solution Approach 1:
A micro-lens is introduced as an intermediary optical element positioned above the micro-LED. The micro-lens has a lateral size larger than the micro-LED and a specific focal length that focuses light at the front surface of the micro-LED, thereby improving light extraction efficiency without requiring changes to the micro-LED structure itself.
Solution Approach 2:
The solution moves from modifying the micro-LED in the lateral dimension to adding an optical element in the vertical dimension. By positioning the micro-lens above the micro-LED with a controlled spacer layer thickness, the system exploits the third dimension (vertical spacing) to achieve improved light extraction while maintaining the small lateral footprint of the micro-LED.
2Loss of energy
If micro-lens lateral size is increased to improve light collection, then light extraction efficiency is improved, but device area and packing density are compromised
Solution Approach 1:
The micro-lens is designed with specific parameter ratios: lateral size of 1.5-3 times the micro-LED size, and focal length of 1-3 times the micro-LED lateral size. These optimized parameters enable efficient light collection while minimizing the area overhead, achieving collected LEE of 10% or more without excessive area increase.
3Loss of energy
If spacer layer thickness is optimized to position focal point at micro-LED surface, then light collimation and extraction are improved, but device complexity and manufacturing precision requirements increase
Solution Approach 1:
The spacer layer thickness is optimized to be 0.5-3 times the micro-LED lateral size, with the micro-lens focal length set to 1-3 times the micro-LED lateral size. This parameter optimization positions the focal point at or near the front surface of the micro-LED, achieving effective light collimation and extraction while establishing clear design guidelines for manufacturing.
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 configuration significantly increases the collected light extraction efficiency to about 10% within a specific emission angle range, improving the overall light extraction and coupling efficiency for display systems.
Implementation Method 1
a micro-lens on the spacer layer and configured to extract and collimate the light emitted by the micro-LED
Implementation Method 2
Light emitting diodes (LEDs) convert electrical energy into optical energy
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed herein are techniques for micro-light emitting diodes (micro-LEDs). According to certain embodiments, a micro-LED device includes a micro-LED comprising a semiconductor mesa structure configured to emit light, a spacer layer on the micro-LED, and a micro-lens on the spacer layer and configured to extract and collimate the light emitted by the micro-LED, where a thickness of the spacer layer is selected such that a focal point of the micro-lens is at a front surface of the semiconductor mesa structure.