Nano-Photonic LED Emitters for Surface Mode Light 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 and energy loss due to surface waves, leading to lower external quantum efficiency (EQE) at high current densities and temperatures.
Innovation Solution
The integration of patterned layers, such as hyperbolic metamaterials or low refractive index materials, with a metal back reflector and indium tin oxide (ITO) layers in LED cavities to transform surface modes into directional radiation, reducing ohmic losses and enhancing Purcell factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high current density is applied to increase light output, then luminous brightness is improved, but internal quantum efficiency drops due to droop mechanisms
Solution Approach 1:
The patent changes the optical mode parameters by introducing hyperbolic metamaterials that support high-momentum photonic modes. This transforms the radiation characteristics from conventional low-momentum modes to high-momentum modes, enabling efficient light extraction at high current densities without suffering from droop mechanisms. The metamaterial layer modifies the density of optical states and momentum distribution of emitted photons.
Solution Approach 2:
The patent employs a composite structure combining conventional LED materials with hyperbolic metamaterials. The metamaterial layer, composed of alternating metal and dielectric nanoscale layers, creates unique optical properties that enhance light extraction. This composite approach integrates the light-generating capability of MQWs with the enhanced optical mode control of metamaterials.
2Device complexity
If conventional LED structures are used, then device simplicity is maintained, but energy is trapped as surface waves and dissipated through ohmic losses
Solution Approach 1:
The hyperbolic metamaterial layer acts as an intermediary between the multiple quantum wells and the external environment. It mediates the conversion of surface-bound electromagnetic modes into propagating radiation modes. The metamaterial's unique dispersion relation enables coupling between evanescent surface waves and radiative modes, facilitating energy extraction that would otherwise be lost.
Solution Approach 2:
The patent introduces a new dimensional aspect to light extraction by utilizing the hyperbolic dispersion relation in momentum space. The metamaterial enables access to high-momentum states that are unavailable in conventional isotropic materials, effectively adding a new dimension to the optical mode space and enabling efficient extraction of previously trapped energy.
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 increases external quantum efficiency by coupling near-field radiation into high-momentum modes, improving light extraction and brightness while reducing droop-related efficiency drops at high current densities and temperatures.
Implementation Method 1
The patterned layer may be a hyperbolic metamaterials (HMM) layer
Implementation Method 2
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
the plasmonic antenna array is configured to support surface lattice resonances at a first wavelength, arising from diffractive coupling of localized surface plasmon resonances
Implementation Method 6
support surface lattice resonances at a first wavelength
Implementation Method 7
increases external quantum efficiency by coupling near-field radiation into high-momentum modes
Data Source
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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.