Micro LED Mesa Slope for Light Extraction Efficiency
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Solution Overview
Problem
Micro light emitting elements experience a significant drop in light emission efficiency when miniaturized below 10 μm, resulting in low external quantum efficiency, which is a critical issue for achieving high brightness and long-term reliability in display devices.
Innovation Solution
A micro light emitting element is designed with a nitride semiconductor layer comprising an N-side layer, a light emission layer, and a P-side layer, where micro-mesas with a flat top surface and inclined slope are formed on the P-side layer to surround the light emission layer, enhancing light extraction efficiency. The manufacturing method involves laminating the layers on a growth substrate, forming micro-mesas before bonding to a driving circuit substrate, and etching to create a slope angle within a prescribed range, including 45°, to improve light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If micro light emitting elements are miniaturized below 10 μm, then the display resolution and pixel density are improved, but the light emission efficiency drops significantly
Solution Approach 1:
The invention introduces a slope structure (curved surface) on the light emission surface of the micro light emitting element. This slope causes light to be emitted at various angles rather than perpendicular to a flat surface, effectively increasing the extraction efficiency of light that would otherwise be trapped by total internal reflection. This curvature modification resolves the contradiction by maintaining high light emission efficiency even when the element size is miniaturized below 10 μm.
Solution Approach 2:
The invention applies the slope structure selectively to specific regions of the light emitting element, creating local structural variation that optimizes light extraction without affecting the entire device. By modifying only the light emission surface with a slope while keeping other structures compact, the invention achieves high light extraction efficiency in the critical emission region while maintaining the miniaturized overall structure.
2Length of moving object
If the size of micro light emitting elements is reduced, then the pixel pitch is decreased and display fineness is improved, but the external quantum efficiency is reduced
Solution Approach 1:
The slope structure modifies the light emission surface to emit light at multiple angles, increasing the probability that photons escape the semiconductor material. This curvature effect compensates for the reduced light extraction area in miniaturized elements, maintaining external quantum efficiency even when pixel pitch is reduced below 10 μm.
Solution Approach 2:
The invention introduces a dimensional change by creating a three-dimensional slope structure on the otherwise two-dimensional light emission surface. This adds a angular dimension to light emission, allowing photons to escape at various angles rather than only perpendicular to the surface, thereby maintaining high external quantum efficiency in miniaturized elements.
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 significantly increases light output by improving light extraction efficiency, with the micro light emitting element achieving 190% of the output compared to a comparative example without micro-mesas, while maintaining internal quantum efficiency and reducing internal quantum efficiency loss due to current density and etching effects.
Implementation Method 1
the slope being a surface extended from the P-side layer to a part of the N-side layer and being inclined at an angle within a prescribed range including 45° with respect to the light emission layer
Data Source
AI summary
[Object] To provide a micro LED element that can reduce deterioration in light emission efficiency, even when the micro LED element is miniaturized in size.[Solution] A micro LED element (100) includes: a nitride semiconductor layer (14) including an N-side layer (11), a light emission layer (12), and a P-side layer (13); and a plurality of micro-mesas each having a slope that surrounds the light emission layer (12) and is inclined at an angle within a prescribed range including 45° as an angle (θ) formed by the slope and the light emission layer, and a flat portion formed by a surface of the P-side layer.