Corner Mesa RGB Micro-LED Stack for Leakage and Surface Recombination
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Solution Overview
Problem
Traditional LEDs with mesa structures face issues of reduced internal quantum efficiency due to exposed active layers, surface recombination, and leakage current, leading to structural defects and reduced lifespan.
Innovation Solution
The development of an RGB micro-light-emitting diode with a vertically-stacked structure and corner mesa contact structures, which minimizes active layer exposure through perpendicular etching, reducing surface recombination and facilitating easier manufacturing by forming contact structures that enhance electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional mesa structure is used for LED manufacturing, then manufacturing process is simplified, but active layers are exposed to outside causing reduced internal quantum efficiency
Solution Approach 1:
The patent transitions from a planar mesa structure to a vertically-stacked three-dimensional structure. Multiple light-emitting structures (red, green, blue LEDs) are stacked vertically along the growth direction, with each structure having its own active layer enclosed within the stack. This vertical stacking allows the active layers to be positioned internally rather than exposed at the surface, resolving the contradiction between manufacturing simplicity and internal quantum efficiency.
2Ease of manufacture
If traditional mesa structure with etching is used, then manufacturing is easier, but exposed regions are susceptible to leakage current due to surface damage and contamination
Solution Approach 1:
The vertical stacking architecture moves the active layers away from the exposed surface regions. The etched mesa structure now exposes only the peripheral regions and contact areas, while the active layers remain protected within the vertical stack interior. This spatial separation in the vertical dimension protects against plasma damage and contamination affecting leakage current.
Solution Approach 2:
The patent employs passivation layers (such as silicon nitride or silicon oxide) as protective thin films covering the exposed surfaces and peripheral regions. These dielectric layers act as barriers against moisture, oxygen, and plasma contamination, preventing surface damage that would lead to leakage current while allowing the mesa structure to maintain its manufacturing advantages.
3Ease of manufacture
If traditional mesa structure is used, then manufacturing process is simpler, but surface recombination generates heat causing structural defects and reduced lifespan
Solution Approach 1:
By stacking multiple light-emitting structures vertically, the active layers are positioned away from the heat-generating exposed surfaces. The vertical stack geometry allows heat to dissipate through the substrate and contact structures rather than accumulating at the surface, reducing thermal stress and preventing dark line defects that reduce LED lifespan.
Solution Approach 2:
Passivation layers are deposited on the exposed mesa surfaces to provide thermal isolation and protect against environmental factors. These thin film layers reduce surface recombination rates and prevent heat generation at exposed regions, thereby preventing structural defects and extending LED operational life while maintaining the simplicity of the mesa fabrication process.
4Reliability
If vertically-stacked structure with corner mesa contact structures is used, then active layer exposure is minimized improving efficiency, but device structure becomes more complex
Solution Approach 1:
The vertical stacking of multiple light-emitting structures creates a three-dimensional architecture where active layers are enclosed within the stack rather than exposed at the surface. This vertical arrangement minimizes active layer exposure to the environment while maintaining manufacturing feasibility through sequential layer deposition and etching processes.
Solution Approach 2:
The device is segmented into multiple discrete light-emitting structures (red, green, blue LEDs) stacked vertically, each with its own active layer, contact structures, and encapsulation. This segmentation allows each layer to be independently optimized and manufactured, then assembled into the final vertical stack, managing complexity through modular construction.
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 approach increases the lifespan of the micro-light-emitting diode by minimizing surface recombination and improving light emission efficiency, while allowing for individual control of light-emitting structures through current blocking layers.
Implementation Method 1
etching a vertically-stacked structure comprising a substrate, an n-type contact electrode layer, a first light-emitting structure, a first tunnel junction layer, a common electrode layer, a second tunnel junction layer, a second light-emitting structure, and a third light-emitting structure, which are sequentially stacked
Implementation Method 2
electrically connecting the contact structures by passivation and metal contact deposition
Implementation Method 3
electrically connecting the contact structures by passivation and metal contact deposition
Implementation Method 4
A light-emitting diode (LED) is a semiconductor device that emits light when a current flows in the forward direction
Implementation Method 5
A light-emitting diode (LED) is a semiconductor device that emits light when a current flows in the forward direction
Data Source
AI summary
The present inventive concept relates to an RGB micro-light-emitting diode having a vertically-stacked structure with corner mesa contact structures, and a manufacturing method thereof. The RGB micro-light-emitting diode having a vertically-stacked structure with corner mesa contact structures includes an n-type contact electrode layer, a first light-emitting structure, a common electrode layer, a second light-emitting structure, a tunnel junction layer, and a third light-emitting structure, which are sequentially stacked on a substrate. The RGB micro-light-emitting diode with a reduced unit area can be easily manufactured by forming the corner mesa contact structure on each of the n-type contact electrode layers by etching the vertically-stacked structure, forming contact structures on the n-type contact electrode layers, followed by electrical connection.