Group III Nitride Template for Low Dislocation Density
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Solution Overview
Problem
Group III-Nitride semiconductor-based deep ultraviolet LEDs face challenges in manufacturing due to lattice and thermal mismatch defects, leading to high dislocation densities and reduced efficiency, with existing defect mitigation techniques being ineffective for aluminum-containing materials and resulting in increased manufacturing costs and heat build-up.
Innovation Solution
A process involving the growth of Group III nitride layers on a substrate with a patterned metal layer, where a thin metal layer is annealed to form nanoscale islands, reducing lattice defects through lateral overgrowth, and repeated layer pairs are grown to create a smoother, lower-defect template for semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional epitaxial growth methods are used on sapphire, silicon carbide, or silicon substrates, then semiconductor layers can be grown, but high dislocation densities (10^8/cm^2 to 10^16/cm^2) result due to lattice and thermal mismatch
Solution Approach 1:
The patent segments the growth process into two distinct phases: initial layer growth on the substrate, followed by lateral overgrowth that propagates defect-free regions across the surface. This segmentation allows the system to overcome the inherent substrate defects by creating new, defect-free crystal regions that laterally cover the defective substrate areas.
Solution Approach 2:
The patent transitions from vertical growth (perpendicular to substrate) to lateral growth (parallel to substrate surface). This dimensional change enables the semiconductor layer to propagate over the substrate defects without inheriting them, as the growth front moves laterally across the surface rather than vertically through the defective substrate interface.
2Manufacturing precision
If epitaxial lateral overgrowth (ELOG) is used to reduce dislocation density, then defect density decreases to 10^5/cm^2 to 10^6/cm^2, but aluminum-containing materials cannot be grown effectively due to aluminum sticking to masked material
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the substrate and the aluminum-containing semiconductor layer. This buffer layer prevents direct interaction between aluminum and the masked material, eliminating the sticking problem while still enabling lateral overgrowth to reduce dislocation density.
Solution Approach 2:
The patent modifies the growth conditions and layer composition parameters to enable lateral overgrowth of aluminum-containing materials. By adjusting these parameters, the system overcomes the aluminum-sticking issue and achieves effective growth of high-quality aluminum nitride and related compounds.
3Manufacturing precision
If multiple defect mitigation techniques are applied, then dislocation density is reduced, but manufacturing costs increase and heat build-up occurs
Solution Approach 1:
The patent extracts and eliminates the need for complex multi-step defect mitigation processes by implementing a simplified lateral overgrowth approach. This single effective mechanism replaces multiple sequential processing steps, reducing manufacturing complexity while achieving the same defect reduction goals.
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 process significantly reduces dislocation density and improves the quality of semiconductor devices by creating a smoother, flatter surface for growing light-emitting diodes or sensors, enhancing their efficiency and operational performance in the deep ultraviolet range.
Implementation Method 1
a thin metal layer is annealed to form nanoscale islands
Implementation Method 2
a thin metal layer is annealed to form nanoscale islands
Implementation Method 3
growth of Group III nitride layers on a substrate with a patterned metal layer
Implementation Method 4
reducing lattice defects through lateral overgrowth
Data Source
AI summary
A template for a semiconductor device is made by providing an AGN substrate, growing a first layer of Group III nitrides on the substrate, depositing a thin metal layer on the first layer, annealing the metal such as gold so that it agglomerates to form a pattern of islands on the first layer; transferring the pattern into the first layer by etching then removing excess metal; and then depositing a second Group III nitride layer on the first layer. The second layer, through lateral overgrowth, coalesces over the gaps in the island pattern leaving a smooth surface with low defect density. A Group III semiconductor device may then be grown on the template, which may then be removed. Chlorine gas may be used for etching the pattern in the first layer and the remaining gold removed with aqua regia.