UV LED Array Using Segmented N-Layers for Resistance Reduction
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Solution Overview
Problem
Current ultraviolet light-emitting diodes (UV LEDs) face limitations in light intensity, size, and reliability due to high resistance in Group III nitride semiconductor layers, defects from lattice and thermal mismatch, and poor thermal conductivity of substrates, which restricts their application in high-density optical disk devices and purification systems.
Innovation Solution
A deep ultraviolet light-emitting array is developed using an AlxInyGa1-x-yN quantum-well active region on a template with a patterned substrate, employing pulsed lateral overgrowth techniques and a thick, doped or undoped AlInGaN layer for reduced defect density and enhanced strain relief, along with a superlattice structure for improved optical transparency and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the aluminum content in AlxGa1-xN layers is increased to achieve higher light intensity, then the resistance in the layer increases, rendering the structure insufficient
Solution Approach 1:
The patent divides the n-type layer into multiple thinner sub-layers (e.g., two 50nm layers instead of one 100nm layer) to reduce the resistance in high-aluminum-content regions. This segmentation allows each sub-layer to have optimized thickness and aluminum composition, achieving lower overall resistance while maintaining the required light intensity from high-aluminum AlGaN layers.
Solution Approach 2:
The patent applies different aluminum compositions and layer thicknesses at different locations within the n-type region. High-aluminum-content layers are used where light intensity is needed, while thinner or lower-aluminum sub-layers are used where electrical conduction is critical, creating local optimization of both optical and electrical properties.
2Illumination intensity
If individual distinct LED's are combined into an array to increase light intensity, then the number of connections and assembly cost increase significantly
Solution Approach 1:
The patent merges multiple LED structures into a single integrated array on one substrate. Multiple quantum well regions are formed in parallel within the same device structure, sharing common n-type and p-type contact layers. This eliminates the need for separate connections for each LED, reducing assembly complexity while maintaining high total light intensity.
Solution Approach 2:
The patent creates a multi-functional structure where a single device performs the function of multiple LEDs. The array structure allows one device to provide both individual LED functionality and collective high-intensity output, eliminating redundant connection infrastructure.
3Area of stationary object
If the path length for current flow is extended to increase array size, then the resistance in the n-type layer prohibits extensive path length
Solution Approach 1:
The patent segments the n-type layer into multiple thin sub-layers arranged in a stepped or interleaved configuration. This segmentation reduces the effective current path length through high-resistance regions while allowing the overall device area to be extended. Current can flow through multiple parallel paths in the segmented structure, reducing total resistance.
Solution Approach 2:
The patent transitions from a planar layer structure to a three-dimensional stepped or interleaved arrangement of n-type sub-layers. This dimensional change allows current to flow through multiple levels and parallel paths, effectively reducing resistance while enabling larger device area. The stepped configuration creates multiple current flow pathways that reduce the equivalent resistance.
4Reliability
If defects from lattice and thermal mismatch are present in Group III nitride LEDs, then the efficiency and lifetime of LEDs are reduced
Solution Approach 1:
The patent introduces intermediate buffer layers and transition layers between the substrate and the active AlGaN regions. These intermediary layers gradually transition the lattice constant and thermal properties, reducing mismatch stresses and preventing dislocation formation. The buffer layers act as mediators that absorb the harmful effects of lattice and thermal mismatch.
Solution Approach 2:
The patent changes the compositional parameters of the semiconductor layers, using graded aluminum composition in buffer layers (e.g., Al0.1Ga0.9N transitioning to Al0.3Ga0.7N) to gradually match lattice constants. This parameter gradient reduces dislocation density by minimizing abrupt lattice mismatches, thereby improving LED efficiency and lifetime.
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 results in a higher quality, more reliable, and robust UV LED array with increased light intensity and extended lifetime, capable of operating at higher drive currents and temperatures, addressing the limitations of existing UV LEDs.
Implementation Method 1
A deep ultraviolet light-emitting array is developed using an AlxInyGa1-x-yN quantum-well active region
Implementation Method 2
employing pulsed lateral overgrowth techniques and a thick, doped or undoped AlInGaN layer for reduced defect density
Data Source
AI summary
An ultra-violet light-emitting diode (LED) array, 12, and method for fabricating same with an AlInGaN multiple-quantum-well active region, 500, exhibiting stable cw-powers. The LED includes a template, 10, with an ultraviolet light-emitting array structure on it. The template includes a first buffer layer, 321, then a second buffer layer, 421, on the first preferably with a strain-relieving layer in both buffer layers. Next there is a semiconductor layer having a first type of conductivity, 500, followed by a layer providing a quantum-well region, 600, with an emission spectrum ranging from 190 nm to 369 nm. Another semiconductor layer having a second type of conductivity is applied next, 800. A first metal contact, 980, is a charge spreading layer in electrical contact with the first layer and between the array of LED's. A second contact, 990, is applied to the semiconductor layer having the second type of conductivity, to complete the LED.