Ultra-Thin GaN Quantum Heterostructures for DUV-LED Efficiency
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Solution Overview
Problem
Deep ultra-violet light-emitting diodes (DUV-LEDs) face challenges with low external and internal quantum efficiency due to lattice mismatch, poor doping efficiency, total internal reflection, and polarization properties, particularly for wavelengths shorter than 240 nm, limiting their application and performance.
Innovation Solution
The use of ultra-thin GaN/AlN quantum heterostructures with tunable geometry and epitaxial deposition parameters to enhance wavefunction overlap and light extraction, along with a layered structure design that includes strain relaxation and graded injection layers to improve carrier injection efficiency and tunable wavelength emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If AlGaN multi-quantum well light-emitting active regions are used for DUV emission, then light generation is achieved, but external quantum efficiency drops particularly for wavelengths shorter than 240 nm
Solution Approach 1:
The patent changes the material composition parameters by using AlGaN with aluminum content x in the range of 0.25 to 0.75, and employs quantum well thicknesses of 2-10 nm to optimize the bandgap and emission wavelength. This parameter optimization resolves the contradiction by achieving high external quantum efficiency across the DUV spectrum including wavelengths below 240 nm through precise control of aluminum content and quantum well dimensions
Solution Approach 2:
The patent employs composite AlGaN/AlN heterostructure materials where AlGaN layers with specific aluminum content are combined with AlN barrier layers. This composite material approach enables tailored bandgap engineering and effective mass reduction, resolving the efficiency-wavelength performance contradiction by creating optimized light-emitting regions that maintain high external quantum efficiency at short wavelengths
2Ease of manufacture
If non-native substrates are used, then device fabrication is enabled, but large lattice mismatch creates high dislocation densities
Solution Approach 1:
The patent segments the light-emitting active region into multiple thin quantum well layers (2-10 nm each) separated by AlN barrier layers. This segmentation distributes and isolates dislocation defects within individual layers, preventing their propagation across the entire structure. The segmented quantum well architecture enables use of non-native substrates while maintaining low effective dislocation density in the active regions
Solution Approach 2:
The patent introduces AlN barrier layers as intermediary structures between the non-native substrate and the AlGaN quantum wells. These intermediary layers act as dislocation filters and strain management layers, enabling fabrication on non-native substrates while protecting the active quantum well regions from high dislocation densities
3Use of energy by moving object
If AlGaN quantum well/barrier heterostructures are used for DUV emission, then light generation is achieved, but light extraction efficiency is limited due to total internal reflection
Solution Approach 1:
The patent applies local quality optimization by creating specific structural features at the light-extraction interface, including patterned contact layers and surface texturing in the p-AlGaN contact region. These localized structural modifications create preferential light extraction pathways that reduce total internal reflection losses at critical interfaces without affecting the bulk heterostructure performance
4Length of moving object
If high aluminum content is used in AlGaN active region, then DUV emission wavelength is achieved, but polarization properties make light extraction difficult
Solution Approach 1:
The patent employs dynamic carrier confinement and population control in the quantum well structures, where carriers are dynamically confined in the AlGaN wells with aluminum content optimized for DUV emission. The quantum confinement effect dynamically adjusts the effective mass and density of states, enabling DUV wavelength emission while managing polarization effects through controlled carrier distribution in the quantum well states
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 results in high internal quantum efficiency and tunable wavelength DUV-LEDs with enhanced light extraction and reduced carrier injection losses, enabling efficient deep UV emission across a 219-280 nm range.
Implementation Method 1
ultra-thin quantum heterostructures configured to control the photon emission wavelength
Implementation Method 2
light emitting diodes (LEDs)
Implementation Method 3
epitaxial deposition time
Implementation Method 4
deposited GaN layer in high vacuum during the epitaxy
Data Source
AI summary
A DUV-LED including a bottom substrate, a n-contact/injection layer formed on the bottom substrate, a p-contact region, and an emitting active region between the n-contact/injection layer and the contact region. The emitting active region includes at least one GaN quantum heterostructure. The at least one GaN quantum heterostructures is sized and shaped to determine a certain emission wavelength. Preferably, the certain emission wavelength is in a range of approximately 219-280 nm. In one embodiment, the size is controlled by precisely controlling parameters selected from the group consisting of: an epitaxial deposition time; a Ga/N ratio; a thermal annealing time; a temperature during deposition; and combinations thereof.