Micro LED Ion-Implanted Sidewalls for EQE Loss Reduction
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Solution Overview
Problem
Micro light-emitting diodes (LEDs) face efficiency droop effects due to non-radiative recombination at the sidewalls, especially when the size is less than 50 micrometers, leading to a substantial decrease in external quantum efficiency (EQE).
Innovation Solution
The design includes an epitaxial structure with a first ion implantation region having a specific depth and angle, and an insulating layer covering the sidewalls, which reduces non-radiative recombination and improves the dangling bond on the sidewall caused by dry etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of micro LED is reduced to increase pixel density, then the display resolution is improved, but the external quantum efficiency substantially decreases due to increased proportion of carriers flowing through the damaged sidewall
Solution Approach 1:
A passivation layer is introduced as an intermediary substance between the damaged sidewall and the carrier flow. This passivation layer fills the damaged sidewall structure and provides a pathway that redirects carriers away from the non-radiative recombination sites, thereby maintaining high external quantum efficiency even in sub-50 micrometer micro LEDs
Solution Approach 2:
The damaged sidewall structure, which initially causes non-radiative recombination and efficiency loss, is converted into a beneficial structure by filling it with passivation material. The damaged morphology is transformed into a carrier-redirection pathway that actively prevents carrier loss, turning the harmful sidewall damage into a protective feature
2Ease of manufacture
If the etching process is used to create mesa and isolation structures, then the device fabrication is achieved, but the sidewall is damaged causing non-radiative recombination
Solution Approach 1:
The passivation layer is applied in advance to cover and protect the sidewall structure before subsequent processing steps. This preliminary protective action prevents further damage to the sidewall during manufacturing processes and establishes a foundation for maintaining sidewall integrity throughout fabrication
Solution Approach 2:
The damaged sidewall structure resulting from etching is transformed into a beneficial configuration by filling it with passivation material. The irregular damaged morphology becomes a carrier-redirection pathway that prevents non-radiative recombination, converting the manufacturing defect into a performance-enhancing feature
3Power
If the current density is increased to improve luminous output, then the power output is improved, but the external quantum efficiency decreases due to efficiency droop effect
Solution Approach 1:
The passivation layer acts as an intermediary that mediates between the high current density input and the light emission output. By providing a controlled pathway for carrier flow through the passivation-filled sidewall structure, it ensures that increased current density translates to proportional increases in luminous output without the typical efficiency droop, maintaining high external quantum efficiency across different power levels
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 design effectively increases the external quantum efficiency and luminous efficiency of micro LEDs by reducing non-radiative recombination and improving the sidewall quality.
Implementation Method 1
The epitaxial structure has a first ion implantation region
Data Source
AI summary
A micro light-emitting diode includes an epitaxial structure and an insulating layer. The epitaxial structure includes a first type semiconductor layer, a light-emitting layer, and a second type semiconductor layer, and has a first ion implantation region. A first distance is present between a surface of the first type semiconductor layer and a top surface of the light-emitting layer adjacent to the surface. A second distance is present between the surface of the first type semiconductor layer and a first bottom side of the first ion implantation region. The second distance is greater than the first distance and less than a height of a mesa. A first included angle having an absolute value between 0 and 15 degrees is present between a first extension direction of a first inner side of the first ion implantation region and a normal direction of the light-emitting layer.