Epitaxial Regrowth Passivation for LED Mesa Surface Recombination
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Solution Overview
Problem
As the physical size of light emitting diodes (LEDs) decreases, efficiency losses due to surface recombination become significant, primarily caused by etched mesa facets with surface imperfections that increase surface recombination velocity, leading to reduced light converting efficiency.
Innovation Solution
A regrowth of an epitaxial layer is used to passivate the etched facets of the LED mesa, creating an improved crystalline interface that reduces dangling bonds and surface imperfections, thereby mitigating surface recombination velocity and efficiency losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the physical size of LEDs is reduced, then device miniaturization is achieved, but surface recombination losses increase significantly
Solution Approach 1:
The patent applies local quality by selectively treating only the mesa facet surfaces with epitaxial regrowth, rather than modifying the entire LED structure. This localized approach addresses the surface recombination problem at the specific location where it occurs most severely (the etched mesa facets), while preserving the overall miniaturized device dimensions and other functional characteristics.
Solution Approach 2:
The patent employs composite materials by growing an epitaxial regrowth layer with different material composition and crystal structure than the underlying etched mesa facets. This regrowth layer, having superior crystalline quality and different surface properties, is deposited on top of the original semiconductor material to create a composite structure that reduces surface recombination while maintaining device miniaturization.
2Shape
If etched mesa facets are created, then device structure is formed, but surface imperfections increase leading to higher surface recombination velocity
Solution Approach 1:
The patent applies preliminary action by performing epitaxial regrowth on the etched mesa facets before final device assembly and operation. This pre-treatment process addresses surface imperfections and reduces surface recombination velocity in advance, ensuring that the mesa structure is properly prepared and optimized before the LED is put into service, thereby improving surface quality without compromising the necessary mesa shape.
3Loss of energy
If surface recombination velocity is high, then non-radiative recombination increases, but light converting efficiency decreases
Solution Approach 1:
The patent applies parameter changes by modifying the surface properties of the mesa facets through epitaxial regrowth. This process changes critical parameters such as surface roughness, crystal orientation, and surface state density, thereby reducing surface recombination velocity and minimizing non-radiative recombination losses, which directly improves light converting efficiency.
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
The regrowth of the epitaxial layer significantly reduces surface recombination velocity, enhancing the efficiency of LEDs by minimizing non-radiative recombination and improving overall light emitting performance.
Implementation Method 1
Regrowth of epitaxial layer for surface recombination velocity reduction in light emitting diodes
Data Source
AI summary
Disclosed herein are methods, systems, and apparatuses for an light emitting diode (LED) array apparatus. In some embodiments, the LED array apparatus may include a plurality of mesas etched from a layered epitaxial structure. The layered epitaxial structure may include a P-type doped semiconductor layer, a active layer, and an N-type doped semiconductor layer. The LED array apparatus may also include one or more regrowth semiconductor layers, including a first regrowth semiconductor layer, which may be grown epitaxially over etched facets of the plurality of mesas. In some cases, for each mesa, the first regrowth semiconductor layer may overlay etched facets of the P-type doped semiconductor layer, the active layer, and the N-type doped semiconductor layer, around an entire perimeter of the mesa.