Epitaxial Lateral Overgrowth for III-Nitride Dislocation Reduction
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Solution Overview
Problem
Existing semiconductor technologies face challenges in achieving high crystal quality due to undesirable dislocation densities in III-nitride materials like GaN, which are exacerbated by the limited availability of suitable substrates with matching crystal properties.
Innovation Solution
The method involves enhancing and terminating dislocations in the underlying semiconductor surface by growing an intermediate layer that enlarges dislocation pits and promotes their intersection, followed by a lateral growth layer to enclose and reduce dislocation propagation, using techniques such as epitaxial lateral overgrowth and discontinuous dielectric masking to minimize dislocation density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional epitaxial growth methods are used on standard substrates, then the growth process is simple and fast, but the resulting semiconductor layers have high dislocation density and poor crystal quality
Solution Approach 1:
The growth process is divided into multiple stages: initial layer growth, buffer layer formation, and final device layer growth. Each stage uses different growth conditions and parameters to address specific requirements, allowing progressive improvement of crystal quality while managing process complexity systematically
Solution Approach 2:
Buffer layers and surface treatments are applied before growing the final device layers. These preliminary actions prepare the substrate surface to reduce dislocation propagation and improve nucleation conditions, thereby enhancing crystal quality of subsequent layers without requiring complete substrate replacement
2Manufacturing precision
If buffer layers and surface treatments are applied to reduce dislocations, then crystal quality improves, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
Growth parameters such as temperature, pressure, and gas flow rates are dynamically adjusted during different stages of epitaxial growth. By optimizing these parameters for each specific growth phase, the process achieves both high crystal quality and maintained productivity without requiring excessive buffer layers or prolonged treatment times
3Manufacturing precision
If dislocations are enhanced and terminated using intermediate layers, then surface dislocation uniformity improves, but the number of growth steps increases
Solution Approach 1:
Intermediate buffer layers serve as mediators between the substrate and final device layers. These buffer layers are specifically designed to enhance and terminate dislocations through controlled growth conditions, providing uniform surface dislocation distribution while absorbing the complexity of multiple growth steps into a standardized intermediate structure
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 results in semiconductor layers with significantly reduced dislocation density, improving crystal quality and uniformity, and can be applied to various semiconductor materials beyond III-nitrides.
Implementation Method 1
epitaxial growth of high crystal quality structures comprising III-nitride materials
Implementation Method 2
discontinuous dielectric masking to minimize dislocation density
Data Source
Figure 1A~1D
Figure 2
Figure 3A~3D
AI summary
Methods which can be applied during the epitaxial growth of semiconductor structures and layers of III-nitride materials so that the qualities of successive layers are successively improved. An intermediate epitaxial layer is grown on an initial surface so that growth pits form at surface dislocations present in the initial surface. A following layer is then grown on the intermediate layer according to the known phenomena of epitaxial lateral overgrowth so it extends laterally and encloses at least the agglomerations of intersecting growth pits. Preferably, prior to growing the following layer, a discontinuous film of a dielectric material is deposited so that the dielectric material deposits discontinuously so as to reduce the number of dislocations in the laterally growing material. The methods of the invention can be performed multiple times to the same structure. Also, semiconductor structures fabricated by these methods.