Lateral Micro-LED Layout to Limit Sidewall Recombination
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Solution Overview
Problem
Micro-light emitting diodes (micro-LEDs) face low quantum efficiencies due to non-radiative recombination at mesa sidewalls, particularly as their physical dimensions decrease, leading to efficiency reductions and increased peak efficiency operating currents.
Innovation Solution
The design of lateral micro-LEDs where carriers primarily move horizontally within the active region and radiatively recombine at or near the center, reducing non-radiative recombination at sidewalls by positioning the p-type and n-type semiconductor regions on the same side of the active region, thereby minimizing carrier diffusion to sidewall surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the physical dimensions of micro-LEDs are reduced to achieve higher packing density and resolution, then the packing density and resolution are improved, but the quantum efficiency deteriorates due to increased non-radiative recombination at sidewalls
Solution Approach 1:
The patent transitions from a vertical LED structure where current flows through the thickness of the device to a lateral LED structure where current flows horizontally within the plane of the active region. This dimensional change allows carriers to recombine away from the sidewalls, eliminating the dominant non-radiative recombination pathway that plagues vertically-oriented micro-LEDs as their size decreases.
Solution Approach 2:
The invention extracts the harmful sidewall recombination interface from the carrier transport path by reconfiguring the device geometry. In the lateral structure, the current injection regions are positioned such that carriers flow through the active region and recombine in the bulk, away from the sidewall surfaces that cause non-radiative losses.
2Measurement precision
If the physical dimensions of micro-LEDs are reduced, then the resolution is improved, but the quantum efficiency deteriorates due to non-radiative recombination at sidewalls
Solution Approach 1:
By changing from vertical to lateral current flow geometry, the patent enables micro-LEDs to maintain high quantum efficiency at smaller dimensions. The lateral structure allows the active region to be confined laterally for high resolution while carriers still have sufficient path length through the active region to recombine radiatively before reaching any boundaries.
3Volume of moving object
If the physical dimensions of micro-LEDs are reduced, then the device size is improved for high-density displays, but the peak efficiency operating current increases
Solution Approach 1:
The lateral geometry extends the carrier transport path within the active region while maintaining a small device footprint. This allows smaller micro-LEDs to achieve their peak efficiency at lower current densities because carriers have a longer effective path length for radiative recombination, improving the ratio of radiative to non-radiative processes.
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 enhances internal quantum efficiency, maintaining it at levels comparable to macro-LEDs even as the micro-LEDs' physical dimensions shrink, minimizing the impact of size reduction on efficiency.
Implementation Method 1
one or more quantum well layers configured to emit light
Implementation Method 2
Light emitting diodes (LEDs) convert electrical energy into optical energy
Implementation Method 3
non-radiative recombination of carriers at mesa sidewalls
Data Source
AI summary
A lateral micro-light emitting diode includes a first semiconductor layer, an active region on the first semiconductor layer and including one or more quantum well layers configured to emit light, a p-type semiconductor region on a first lateral region (e.g., a central region) of the active region, and an n-type semiconductor region on a second lateral region (e.g., peripheral regions) of the active region, where the n-type semiconductor region and the p-type semiconductor region are on a same side of the active region.