LED Sidewall Passivation for Reduced Non-Radiative Recombination
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Solution Overview
Problem
Micro LEDs experience efficiency degradation due to non-radiative recombination at the sidewalls, which reduces their overall efficiency, especially at low current densities, as a result of unsatisfied bonds, chemical contamination, and structural damage from dry etching.
Innovation Solution
The implementation of sidewall passivation techniques, such as in-situ etching and regrowth, diffusion, and epitaxial growth of passivation layers, to minimize defects and preserve the lattice structure, thereby reducing non-radiative recombination and enhancing radiative efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry etching is used to form LED sidewalls, then manufacturing precision is improved, but non-radiative recombination increases due to structural damage and unsatisfied bonds
Solution Approach 1:
A passivation layer is introduced as an intermediary between the etched sidewall and the external environment. This passivation layer saturates the unsatisfied bonds created by dry etching, eliminating non-radiative recombination centers while preserving the precise sidewall geometry formed by dry etching.
Solution Approach 2:
The harmful effect of dry etching (creating unsatisfied bonds and structural damage) is converted into a benefit by deliberately forming a passivation layer that targets these specific defects. The passivation process transforms the damaged sidewall surface into a controlled, passivated interface that prevents non-radiative recombination.
2Loss of energy
If sidewall passivation is implemented, then non-radiative recombination is reduced, but device complexity increases
Solution Approach 1:
The passivation layer is formed with uniform composition and properties across the entire LED sidewall surface. This homogeneous passivation approach simplifies the overall device structure by using a single, consistent material system rather than complex multi-layer or spatially-varying passivation schemes.
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
These techniques effectively mitigate non-radiative recombination at the sidewalls, increasing the efficiency of micro LEDs by confining the current injection path internally and reducing surface recombination, leading to improved performance, especially at low current densities.
Implementation Method 1
sidewall passivation techniques, such as in-situ etching and regrowth, diffusion, and epitaxial growth of passivation layers, to minimize defects and preserve the lattice structure
Implementation Method 2
epitaxial growth of passivation layers
Implementation Method 3
diffusion
Data Source
Figure 1A~1F
Figure 2~3
Figure 4A~4E
AI summary
LED structures are disclosed to reduce non-radiative sidewall recombination along sidewalls of vertical LEDs including p-n diode sidewalls that span a top current spreading layer, bottom current spreading layer, and active layer between the top current spreading layer and bottom current spreading layer.