Group-III Nitride Epitaxy With Lateral Growth for Low Dislocations
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for growing GaN-based materials on aluminum trioxide substrates using MOCVD technology result in high dislocation densities, which hinder the development of high-voltage resistant GaN-based power devices and long-lasting LEDs, as the dislocation density of GaN-based materials is around 1-3E8/cm^3, necessitating a reduction in dislocation density for improved performance.
Innovation Solution
A method involving the formation of multiple mask layers and epitaxial growth stages to laterally grow group-III-nitride layers, where the second epitaxial growth direction blocks dislocations from extending upward, significantly reducing dislocation density in the subsequent layers, and using materials like GaN, AlN, AlGaN, or InGaN for the epitaxial layers, with optional in-situ growth processes in a single MOCVD device to minimize contamination and process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional MOCVD epitaxial growth is used on aluminum trioxide substrates, then the manufacturing process is simple and straightforward, but the dislocation density of the grown GaN-based materials reaches 1-3E8/cm³ which is too high for high-performance devices
Solution Approach 1:
The epitaxial growth process is divided into multiple stages with different mask layers (first mask layer, second mask layer) and growth conditions. Each stage serves a specific function: the first stage grows initial layers with the first mask, the second stage performs lateral growth to block dislocations, and the third stage completes the structure. This segmentation allows dislocation density to be reduced from 1-3E8/cm³ to below 1E8/cm³ while managing process complexity through systematic division of the growth process.
Solution Approach 2:
The invention transitions from conventional vertical epitaxial growth to lateral epitaxial growth in the second growth stage. By growing the group-III-nitride epitaxial layer laterally along the sidewalls of the mask layer rather than vertically upward, the process blocks dislocations from extending into the final device layer. This dimensional change in growth direction is the key mechanism for reducing dislocation density.
2Reliability
If multiple mask layers and lateral growth stages are implemented, then dislocation density is reduced to below 1E8/cm³, but the epitaxial growth process becomes more complex with multiple formation and growth steps
Solution Approach 1:
The first mask layer and first group-III-nitride epitaxial layer are formed in advance before the critical lateral growth stage. This preliminary structuring creates the necessary sidewall geometry that enables dislocation blocking during the second growth stage. The preliminary action of forming these foundation layers ensures that when lateral growth occurs, dislocations are already positioned to be blocked, thereby improving device reliability without requiring complete process redesign.
Solution Approach 2:
The second mask layer serves as an intermediary structure during the lateral growth stage. It is formed on the first mask layer and provides the template for lateral epitaxial growth. This intermediary mask layer enables the transition from vertical to lateral growth mode and facilitates dislocation blocking while maintaining manufacturing feasibility. The intermediary structure is later removed, having served its purpose in achieving below 1E8/cm³ dislocation density.
3Manufacturing precision
If lateral epitaxial growth is performed to block dislocations, then the quality of GaN-based power devices and LEDs is improved, but the growth time and process steps increase
Solution Approach 1:
The lateral epitaxial growth is performed continuously in the second growth stage without interrupting the MOCVD process. The group-III-nitride epitaxial layer grows laterally along the sidewalls of the second mask layer in a continuous manner, blocking dislocations as they propagate. This continuous lateral growth action achieves high epitaxial layer quality (dislocation density below 1E8/cm³) while minimizing idle time between process steps, thereby reducing overall growth time despite the added complexity.
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 effectively reduces dislocation density in group-III-nitride epitaxial layers, enhancing the performance and reliability of GaN-based semiconductor devices by blocking dislocations during lateral growth, thereby improving the quality of GaN-based power devices and LEDs.
Implementation Method 1
growing and forming a second group-III-nitride epitaxial layer on the substrate and the first mask layer by performing a first epitaxial growth
Data Source
AI summary
A group-III-nitride structure and a manufacturing method thereof are provided. In the manufacturing method, a first mask layer is first formed on a substrate; an uncoalesced second group-III-nitride epitaxial layer is formed by performing a first epitaxial growth with the first mask layer as a mask; and a second mask layer is formed at least on the second group-III-nitride epitaxial layer; a third group-III-nitride epitaxial layer is laterally grown and formed by performing a second epitaxial growth on the second group-III-nitride epitaxial layer with the second mask layer as a mask, where the second group-III-nitride epitaxial layer is coalesced by the third group-III-nitride epitaxial layer; a fourth group-III-nitride epitaxial layer is formed by performing a third epitaxial growth on the third group-III-nitride epitaxial layer.