Nano-Photonic LED Reflector Structure for TM Loss Blocking
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Solution Overview
Problem
The reflectance of typical composite mirror architectures in light emitting diodes (LEDs) is limited by the index contrast between semiconductor and oxide layers, leading to partial absorption of incident light, especially at angles outside the critical cone, and current distributed Bragg reflector (DBR) designs with restricted refractive index contrast fail to fully block incident light efficiently.
Innovation Solution
A reflector structure comprising a one-dimension (1D) distributed Bragg reflective (DBR) layer combined with a two-dimension (2D) or three-dimension (3D) photonic crystal (PhC) or hyperbolic metamaterial (HMM) layer, along with a silver-free bottom metal reflector, to effectively block transverse-magnetic (TM) radiation and enhance reflectance, using materials like silicon dioxide (SiO2), titanium oxide (TiO2), and niobium oxide (Nb2O5), which also acts as a transparent conducting oxide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a distributed Bragg reflector (DBR) structure is placed between the thick oxide layer and the metal reflector, then the reflectance is improved, but the performance gains are limited by the restricted refractive index contrast of practical DBR designs
Solution Approach 1:
The patent transitions from conventional 1D DBR structures to 2D photonic crystal structures, adding spatial dimensionality to achieve superior light blocking performance. The 2D PhC layers provide enhanced reflectance through their periodic lattice structures in two dimensions, overcoming the limitations of 1D DBR index contrast restrictions.
Solution Approach 2:
The patent employs composite material structures combining semiconductor layers with high-refractive-index materials such as titanium oxide (TiO2) and niobium oxide (Nb2O5). These composite structures achieve the necessary refractive index contrast for effective light blocking without requiring complex multi-layer DBR designs.
2Ease of manufacture
If a thick oxide layer separates the semiconductor and metal reflector, then manufacturing is simplified, but light incident at angles outside the critical cone interacts with the metal and gets partly absorbed
Solution Approach 1:
The patent introduces 2D photonic crystal layers as intermediary structures between the oxide layer and metal reflector. These PhC layers act as optical mediators that prevent direct interaction between incident light and the lossy metal reflector, thereby reducing energy absorption while maintaining the protective function of the oxide layer.
Solution Approach 2:
The patent replaces the reliance on thick oxide layers for optical isolation with photonic crystal-based optical isolation. This substitution uses photonic bandgap effects rather than purely geometric/physical separation, achieving superior light blocking with thinner structures.
3Illumination intensity
If silver is used in the bottom metal reflector, then reflectance performance is improved, but reliability at high temperatures and high current densities deteriorates
Solution Approach 1:
The patent changes the material composition parameter of the bottom reflector by eliminating silver and using alternative metal materials that maintain reflectance performance while offering superior thermal and electrical stability under high-temperature and high-current-density operating conditions.
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 configuration significantly increases reflectance, reduces TM polarization-related losses, mitigates light interaction with metal reflectors, and provides reliable performance at high temperatures and high current densities, improving extraction efficiency and color efficiency in LEDs, while eliminating silver usage.
Implementation Method 1
a first layer designed to reflect transverse-electric (TE) radiation emitted by the LED, a second layer designed to block transverse-magnetic (TM) radiation emitted from the LED
Implementation Method 2
The first layer may be a one-dimension (1D) distributed Bragg reflective (DBR) layer
Implementation Method 3
The second layer may be a two-dimension (2D) photonic crystal (PhC), a three-dimension (3D) PhC, and/or a hyperbolic metamaterial (HMM)
Implementation Method 4
a plurality of ITO layers designed to operate as a transparent conducting oxide layer
Implementation Method 5
This configuration significantly increases reflectance, reduces TM polarization-related losses
Data Source
AI summary
A system, method and device for use as a reflector for a light emitting diode (LED) are disclosed. The system, method and device include a first layer designed to reflect transverse-electric (TE) radiation emitted by the LED, a second layer designed to block transverse-magnetic (TM) radiation emitted from the LED, and a plurality of ITO layers designed to operate as a transparent conducting oxide layer. The first layer may be a one-dimension (1D) distributed Bragg reflective (DBR) layer. The second layer may be a two-dimension (2D) photonic crystal (PhC), a three-dimension (3D) PhC, and/or a hyperbolic metamaterial (HMM). The 2D PhC may include horizontal cylinder bars, vertical cylinder bars, or both. The system, method and device may include a bottom metal reflector that may be Ag free and may act as a bonding layer.