Micro LED Sidewall Gating for SRH Recombination Control
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Solution Overview
Problem
Inorganic semiconductor-based micro LEDs suffer from efficiency droop due to high SRH recombination at the p-n diode sidewalls, leading to reduced luminous efficacy and non-uniformity across display panels, which existing sidewall treatments and passivation methods fail to fully address.
Innovation Solution
Implementing active or passive sidewall gating schemes, including capacitive coupling and fixed charge injection, to control the charge status near the sidewalls, thereby reducing defect states and trap density, and tuning the internal quantum efficiency (IQE) for improved emission efficacy and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sidewall treatment and passivation are used to improve internal quantum efficiency, then IQE is improved, but efficiency droop and non-uniformity across display panels persist
Solution Approach 1:
A sidewall gate electrode is introduced as an intermediary component between the sidewall defects and the active region. This electrode, when biased, creates an electric field that acts as a mediator to repel carriers from the sidewall region, thereby reducing SRH recombination at the defective sidewall interface while maintaining high IQE in the active region
Solution Approach 2:
The patent changes the electrical parameter (bias voltage) applied to the sidewall gate electrode to dynamically control the depletion region width and carrier distribution near the sidewalls. By adjusting the bias condition, the system can optimize the balance between reducing efficiency droop and maintaining high IQE across different operating conditions
2Illumination intensity
If operating current is increased to improve luminance, then luminance increases, but luminous efficacy decreases due to efficiency droop
Solution Approach 1:
The sidewall gate electrode is biased in advance to create a depletion region near the sidewalls before carriers are injected into the active region. This preliminary action prevents carriers from accumulating at the defective sidewall interface, thereby maintaining high luminous efficacy even at high operating currents where efficiency droop would normally occur
3Reliability
If sidewall defect density is reduced through passivation, then IQE is improved, but emission uniformity across display panels is not fully achieved
Solution Approach 1:
The sidewall gate electrode provides localized control of the electric field specifically at the sidewall region, allowing different parts of the device to have different charge distributions. This local quality control enables uniform emission across the display panel by ensuring consistent carrier repulsion from sidewalls throughout the device array
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
Sidewall gating enhances micro LED efficiency by suppressing SRH recombination, maintaining high IQE across a wide current density range, and ensuring emission uniformity, thus improving display performance.
Implementation Method 1
applying a bias to a micro LED to control the surface state of the micro LED near the micro LED sidewalls, wherein the bias depletes a minority carrier concentration from the sidewalls
Implementation Method 2
an active layer between the electrode sides in the micro LED
Data Source
AI summary
Display structures and methods of operation with micro light emitting diode (LED) sidewall gating are described. In an embodiment, a display structure includes a vertically oriented micro LED mounted on a display substrate, in which the micro LED includes a p-n diode with top and bottom electrode sides, and a sidewall gate electrode spanning a sidewall of the p-n diode where the active layer is included. In various embodiments, a bias may be applied to the sidewall gate electrode while driving the micro LED to deplete a minority carrier concentration from the sidewall of the p-n diode.