Nano-Photonic LED Emitters for Surface Wave Extraction
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Solution Overview
Problem
Internal quantum efficiency in multiple quantum well light emitting diodes (LEDs) is limited by droop-related mechanisms, leading to lower external quantum efficiency (EQE) at high current densities and temperatures, with energy being trapped as surface waves and dissipated due to ohmic losses.
Innovation Solution
Incorporating a patterned layer, such as a hyperbolic metamaterial or metallic nano-antennas, within the semiconductor layer to transform surface modes into directional radiation, combined with a metal back reflector and indium tin oxide layer to reduce field confinement and ohmic losses, enhancing external quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional LED structures are used, then device simplicity is maintained, but external quantum efficiency is limited due to droop mechanisms and surface wave trapping
Solution Approach 1:
The patent embeds nano-photonic structures (hyperbolic metamaterials, photonic crystals, metallic/dielectric nanoparticles) within the semiconductor layer itself, creating a nested configuration where the active region contains the photonic structures. This integration allows the complex photonic functionality to be housed within the existing LED architecture, improving external quantum efficiency without requiring separate external components
Solution Approach 2:
The patent employs composite material structures combining semiconductor materials with metamaterials (metal-dielectric composites), photonic crystal materials, and various nanoparticle compositions. These composite materials provide both the light-emitting functionality of the semiconductor and the enhanced photonic control of the metamaterials, resolving the contradiction between efficiency improvement and structural simplicity
2Illumination intensity
If high current densities are applied to increase brightness, then luminous output is improved, but internal quantum efficiency decreases due to droop mechanisms
Solution Approach 1:
The patent modifies the photonic parameters of the emitter cavity by introducing nano-photonic structures that change the local density of optical states, Purcell factors, and mode confinement characteristics. These parameter changes enhance radiative recombination rates and improve internal quantum efficiency even at high current densities, counteracting the droop effect through photonic engineering rather than electrical parameter adjustment
3Use of energy by moving object
If surface waves are generated in the active region, then light emission is produced, but energy is lost through ohmic dissipation
Solution Approach 1:
The patent converts the harmful surface waves that cause ohmic losses into beneficial directional radiation through the use of patterned nano-photonic structures. The hyperbolic metamaterials and photonic crystals transform the evanescent surface modes into propagating radiation modes, converting what was previously a loss mechanism into an efficient light extraction pathway that reduces ohmic dissipation while enhancing external quantum 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 solution increases external quantum efficiency by coupling near-field radiation into high-momentum modes, reducing optical losses, and improving light extraction and brightness, thereby addressing the limitations of droop-related mechanisms.
Implementation Method 1
The patterned layer may be one-dimensional, two-dimensional or three-dimensional... The patterned layer may be a hyperbolic metamaterials (HMM) layer and may include Photonic Hypercrystal (PhHc)
Implementation Method 2
a patterned layer configured to transform surface modes into directional radiation
Implementation Method 3
a metal back reflector layer configured to reflect incident radiation
Implementation Method 4
an indium tin oxide (ITO) layer positioned between the semiconductor layer and the metal back reflector layer to reduce field confinement improving the kinetic energy of the carriers near the metal reflector
Implementation Method 5
a low refractive index layer positioned adjacent to the metal back reflector layer to operate in combination with the metal layer to reduce ohmic losses compromising field confinement near the lossy layers to couple the radiation into radiated emissions
Implementation Method 6
a semiconductor layer formed as a III/V direct bandgap semiconductor to produce radiation
Data Source
AI summary
A device, system and method for producing enhanced external quantum efficiency (EQE) LED emission are disclosed. The device, system and method include a patterned layer configured to transform surface modes into directional radiation, a semiconductor layer formed as a III/V direct bandgap semiconductor to produce radiation, and a metal back reflector layer configured to reflect incident radiation. The patterned layer may be one-dimensional, two-dimensional or three-dimensional. The patterned layer may be submerged within the semiconductor layer or within the dielectric layer. The semiconductor layer is p-type gallium nitride (GaN). The patterned layer may be a hyperbolic metamaterials (HMM) layer and may include Photonic Hypercrystal (PhHc), or may be a low or high refractive index material or may be a metal.