Vertical Deep UV LED Strain-Relieved Superlattice
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Solution Overview
Problem
Lateral geometry UV LEDs face current crowding issues due to high resistance in lateral conduction materials, which is exacerbated for deep UV LEDs, leading to inefficiencies and defects in manufacturing.
Innovation Solution
A vertical geometry LED structure is developed with a buffer layer deposited using pulsed atomic layer epitaxy (PALE) growth, eliminating the need for a GaN buffer layer and incorporating a strain-relieved superlattice, allowing for improved substrate removal and reduced resistance, thereby enhancing light output and manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lateral geometry is used for UV LEDs, then manufacturing simplicity is maintained, but current crowding occurs due to high resistance in lateral conduction materials
Solution Approach 1:
The patent transitions from lateral geometry to vertical geometry, changing the current conduction direction from lateral to vertical. This dimensional change eliminates current crowding by allowing current to flow directly through the active region without lateral traversal, resolving the contradiction between manufacturing simplicity and current distribution uniformity.
2Adaptability or versatility
If wavelength of emission is decreased for deep UV LEDs, then application utility is improved, but resistance of lateral conduction material increases
Solution Approach 1:
By changing from lateral to vertical current conduction, the patent eliminates the resistance issue that worsens with decreased wavelength. The vertical geometry allows current to flow directly through the active region without traversing lateral conduction paths, maintaining current conduction efficiency across all UV wavelengths including deep UV.
3Reliability
If vertical geometry is adopted to mitigate current crowding, then current distribution improves, but manufacturing complexity increases
Solution Approach 1:
The vertical LED structure is divided into distinct functional segments: substrate, buffer layer, active region with quantum wells, and contact layers. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall manufacturing feasibility through established epitaxial growth techniques.
Solution Approach 2:
The buffer layer serves as an intermediary between the substrate and the active region, providing lattice matching and reducing dislocation density. This intermediary layer simplifies the manufacturing process by enabling the use of standard substrates while achieving high-quality vertical structures.
4Ease of manufacture
If GaN buffer layer is used in vertical LEDs, then substrate removal is facilitated, but additional manufacturing steps are required
Solution Approach 1:
The buffer layer is designed to undergo phase transition (melting or sublimation) when exposed to laser energy, enabling selective substrate removal. This phase transition property allows the buffer layer to serve as a sacrificial element that can be removed on-demand without affecting other device components, streamlining the manufacturing process.
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 vertical geometry LED design reduces heat generation, increases light output, and mitigates defects, enabling more efficient and reproducible production of deep UV LEDs, particularly suitable for applications like bioaerosol fluorescence detection systems.
Implementation Method 1
After formation of the functional layers the diode is removed from the substrate by laser assist wherein one or more of a series of buffer layers comprising AlxInyGa1-x-yN between the LED and substrate are melted or sublimated
Implementation Method 2
A particular feature of a preferred embodiment of the present invention is the incorporation of a buffer layer that is deposited using a pulsed atomic layer epitaxy (PALE) growth technique
Data Source
AI summary
A vertical geometry light emitting diode with a strain relieved superlattice layer on a substrate comprising doped AlXInYGa1-X-YN. A first doped layer is on the strain relieved superlattice layer AlXInYGa1-X-YN and the first doped layer has a first conductivity. A multilayer quantum well is on the first doped layer comprising alternating layers quantum wells and barrier layers. The multilayer quantum well terminates with a barrier layer on each side thereof. A second doped layer is on the quantum well wherein the second doped layer comprises AlXInYGa1-X-YN and said second doped layer has a different conductivity than said first doped layer. A contact layer is on the third doped layer and the contact layer has a different conductivity than the third doped layer. A metallic contact is in a vertical geometry orientation.