Nested Superlattice UV LED Template for AlGaN Dislocation Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current ultraviolet light-emitting diodes (UV LEDs) face challenges in manufacturing due to high dislocation densities in Group III-nitride semiconductor layers, leading to reduced efficiency and lifetime, particularly for aluminum-containing materials, and existing defect mitigation techniques like epitaxial lateral overgrowth are ineffective for these materials.
Innovation Solution
A deep ultraviolet light-emitting device with a nested superlattice structure comprising undoped or n-type Al1-x-yInyGaxN layers, which reduces defect propagation and strain management, and includes a template with a substrate and nested superlattice, allowing for the growth of high-quality AlGaN layers with reduced dislocation density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Group III-nitride semiconductor layers are grown hetero-epitaxially on substrates such as sapphire, silicon carbide, or silicon, then light-emitting diodes can be fabricated, but high dislocation densities (10^8 to 10^10 cm^-2) arise due to lattice and thermal mismatch, reducing efficiency and lifetime
Solution Approach 1:
The patent introduces an AlN buffer layer as an intermediary between the substrate and the AlGaN active layer. This buffer layer acts as a mediator that absorbs lattice mismatch and thermal expansion differences, preventing dislocation propagation from the substrate into the active region, thereby reducing dislocation density from 10^8-10^10 cm^-2 to lower levels.
Solution Approach 2:
The patent segments the semiconductor structure into distinct functional layers: an AlN buffer layer, an AlGaN active layer with quantum wells, and contact layers. This segmentation allows each layer to be optimized independently for its specific function, with the buffer layer specifically designed to handle substrate mismatch issues.
2Manufacturing precision
If epitaxial lateral overgrowth (ELOG) is used to reduce dislocation density to 10^5 to 10^6 cm^-2, then defect density decreases, but the technique becomes ineffective for aluminum-containing III-Nitride materials due to aluminum sticking to masked material and disrupting lateral overgrowth
Solution Approach 1:
The patent extracts the aluminum-containing active layer growth from the lateral overgrowth process by using a planar growth approach on a patterned buffer layer. Instead of attempting lateral overgrowth through masked regions (which causes Al to stick to the mask), the structure is built vertically with the AlN buffer patterned first, then AlGaN grown planarly over the patterns.
3Reliability
If the nested superlattice structure with AlN buffer layer and AlGaN active layer is implemented, then defect propagation and strain are reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies local quality by making the buffer layer composition spatially varying - AlN (Al-rich) in regions where dislocation blocking is needed, and AlGaN (Ga-rich) in regions where lattice matching is prioritized. This local compositional optimization reduces overall strain and defect propagation without requiring complete structural redesign.
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 nested superlattice structure significantly decreases defect propagation and strain, enabling the growth of high-quality AlGaN layers, thereby improving the power-lifetime performance and efficiency of deep UV LEDs.
Implementation Method 1
nested superlattice structure comprising undoped or n-type Al1-x-yInyGaxN layers, which reduces defect propagation and strain management
Implementation Method 2
a light emitting quantum well region above the first layer comprising Al1-x-yInyGaxN wherein α≦x≦b
Data Source
AI summary
A light emitting device with a template comprising a substrate and a nested superlattice. The superlattice has Al1-x-yInyGaxN wherein 0≦x≦α and 0≦y≦1 with x increasing with distance from said substrate. An ultraviolet light-emitting structure on the template has a first layer with a first conductivity comprising Al1-x-yInyGaxN wherein α≦x; a light emitting quantum well region above the first layer comprising Al1-x-yInyGaxN wherein α≦x≦b; and a second layer over the light emitting quantum well with a second conductivity comprising Al1-x-yInyGaxN wherein b≦x. The light emitting device also has a first electrical contact in electrical connection with the first layer, a second electrical contact in electrical connection with the second layer; and the device emits ultraviolet light.