LED Sidewall Passivation for Micro LED Efficiency
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Solution Overview
Problem
Micro LEDs face efficiency degradation due to non-radiative recombination at the sidewalls, which is exacerbated by structural damage and defects, leading to reduced luminous efficacy, especially at low current densities.
Innovation Solution
The implementation of sidewall passivation techniques and current confinement structures to mitigate non-radiative recombination, including in-situ etching, epitaxial regrowth, diffusion, and the formation of passivation layers to minimize defects and confine current injection internally within the p-n diode layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If micro LEDs are fabricated with standard sidewall structures, then manufacturing is simpler, but non-radiative recombination at sidewalls increases causing efficiency degradation
Solution Approach 1:
Sidewall passivation layers are formed through preliminary actions including in-situ etching, epitaxial regrowth, and diffusion processes before the LED is fully assembled. These preliminary treatments prepare the sidewalls to reduce non-radiative recombination by passivating surface states and preventing carrier leakage, thereby improving efficiency before the device enters operation.
2Loss of energy
If current injection is allowed to spread freely, then ease of operation is improved, but current leakage to sidewalls increases causing efficiency droop
Solution Approach 1:
The patent implements local quality by creating laterally confined current injection regions with different properties from the bulk. Current confinement structures are formed adjacent to the active layer to restrict carrier injection to specific regions, preventing lateral spreading and leakage to sidewalls. This localized control of current injection maintains efficiency by keeping carriers away from non-radiative recombination sites at the sidewalls.
3Use of energy by moving object
If operating current density is increased to overcome efficiency droop, then luminous efficacy increases initially, but efficiency decreases at high current density
Solution Approach 1:
The patent converts the harmful effect of sidewall non-radiative recombination into a beneficial situation by implementing sidewall passivation and current confinement. These structures transform the sidewalls from harmful recombination sites into passivated surfaces that do not degrade performance. By eliminating the harmful sidewall effect through preliminary passivation actions, the LED can operate at lower current densities while maintaining high efficiency, effectively converting what would be a limitation into an advantage.
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 enhance the radiative efficiency of micro LEDs by reducing surface recombination and maintaining the lattice structure, thereby improving luminous efficacy and extending the pre-droop region of the internal quantum efficiency curve.
Implementation Method 1
sidewall passivation techniques to mitigate non-radiative recombination
Implementation Method 2
epitaxial regrowth, diffusion, and the formation of passivation layers to minimize defects
Implementation Method 3
in-situ etching, epitaxial regrowth, diffusion, and the formation of passivation layers
Data Source
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.