Small-Mesa Deep-UV LED Layout for Uniform Current Spreading
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Solution Overview
Problem
Deep-UV LEDs face limitations in performance due to current crowding, thermal management, and inefficient light extraction, primarily attributed to high defect densities in group-III nitride films and high refractive indices of metal nitride materials, leading to non-uniform electron-hole recombination and thermal runaway.
Innovation Solution
The development of deep-UV LEDs with small mesa geometries and resonant microcavities that confine emitted light to fewer than 10 transverse modes, improving current spreading and light extraction by forming mesas with dimensions equal to a small integer number of wavelengths, and incorporating materials like ZnO, MgO, and BN to enhance light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional LED structures with larger mesa widths are used, then light extraction is improved, but current crowding and non-uniform electron-hole recombination occur
Solution Approach 1:
The patent changes the critical parameter of mesa width to a specific range (0.5-2.0 times the wavelength of emitted light) to simultaneously achieve mode confinement and reduced current crowding. This parameter optimization resolves the contradiction by finding the optimal dimension that balances light extraction with uniform current distribution.
Solution Approach 2:
The patent introduces resonant microcavity structures that dynamically control light modes through resonance conditions. The microcavity selectively enhances certain transverse modes while suppressing others, enabling efficient light extraction for specific modes while maintaining uniform current distribution across the active region.
2Productivity
If mesa width is reduced to confine light to fewer transverse modes, then light extraction efficiency improves, but current crowding increases
Solution Approach 1:
The patent optimizes mesa width to specific multiples of the emitted light wavelength (0.5-2.0 times wavelength) to achieve mode confinement while minimizing current crowding. This precise parameter control allows the device to confine light to fewer transverse modes without excessively increasing current density non-uniformity.
3Illumination intensity
If group-III nitride materials are used for deep-UV emission, then desired wavelength is achieved, but high defect densities and high refractive index cause performance limitations
Solution Approach 1:
The patent introduces resonant microcavity structures that dynamically control light extraction by creating resonance conditions. The microcavity selectively enhances specific transverse modes, overcoming the high refractive index limitation of group-III nitride materials and improving light extraction efficiency despite the inherent material properties.
4Quantity of substance
If larger mesa areas are used, then more light can be emitted, but thermal management becomes difficult and hot spots form
Solution Approach 1:
The patent divides the light-emitting structure into multiple discrete mesas with controlled dimensions rather than using a single large mesa. This segmentation allows better thermal management by distributing heat generation across multiple smaller regions, preventing hot spot formation while maintaining sufficient total light emission through the array of mesas.
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 uniform electron-hole recombination, reduced current crowding, improved thermal characteristics, and increased light extraction efficiency, enabling higher light output and efficiency compared to conventional LEDs.
Implementation Method 1
electrons and holes injected from the p-type and n-type regions recombine within the intrinsic region, generating light
Implementation Method 2
the mesa width being smaller than 10 times the target wavelength and confining the emitted light from the light emitting region to fewer than 10 transverse modes
Data Source
AI summary
A method for manufacturing a light emitting device can include providing a substrate, forming a first active layer including a first electrical polarity, forming a light emitting region, forming a second active layer including a second electrical polarity, and forming a first electrical contact layer. The light emitting region can emit light with a target wavelength between 200 nm and 300 nm. A plurality of mesas can be formed, where each mesa can include a portion of the first active layer, the light emitting region, the second active layer, and the first electrical contact layer. A mesa width of each mesa is smaller than twice a current spreading length of the light emitting device. In some cases, the current spreading length is from 400 nm to 5 microns. In some cases, a distance separating the mesas from 1 micron to 10 microns.