III-Nitride Epitaxial Growth Dislocation Reduction
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Solution Overview
Problem
Current methods for fabricating semiconductor structures with III-nitride materials face challenges in achieving high crystal quality due to undesirable dislocation densities, which affect the performance of solid-state devices, and existing techniques often result in non-uniform dislocation distribution and limited dislocation reduction.
Innovation Solution
The method involves enhancing and terminating dislocations on the underlying semiconductor surface by growing an intermediate layer with enhanced surface indentations and promoting the intersection of dislocations, followed by lateral growth over the agglomerated dislocations to reduce dislocation density and achieve uniform distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional epitaxial growth methods are used on standard substrates, then substrate availability is improved, but dislocation density remains high and crystal quality deteriorates
Solution Approach 1:
The method applies preliminary surface treatment to the substrate including nitridization and chemical modifications before epitaxial growth. Buffer layers are grown first to prepare the surface, and dislocations are enhanced and agglomerated in advance before the final GaN layer is deposited, preventing dislocation propagation into the functional layer
Solution Approach 2:
The invention introduces intermediate buffer layers between the substrate and the final GaN layer. These buffer layers serve as mediators that accommodate lattice mismatch and prevent dislocation propagation. The buffer layers are selectively removed or modified to allow controlled dislocation aggregation without affecting the crystal quality of the final device layer
2Manufacturing precision
If in-situ deposition methods with etchants are used to impede dislocation progression, then dislocation reduction is achieved, but process complexity increases
Solution Approach 1:
The method extracts and removes dislocations from the growth path by creating sacrificial buffer layers that are selectively etched away after serving their dislocation-aggregation function. The etching step removes the buffer layer containing aggregated dislocations, leaving behind a clean interface for the final GaN layer growth without requiring complex in-situ etching sequences
Solution Approach 2:
The invention maintains continuous epitaxial growth conditions throughout the process, performing surface treatment, buffer layer growth, and dislocation aggregation in a continuous sequence without breaking vacuum or interrupting the growth environment. This eliminates the need for separate ex-situ etching steps and complex process transitions, reducing overall process complexity while maintaining dislocation reduction effectiveness
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 and improved crystal quality, as the enhanced and intersected dislocations are effectively terminated, leading to a final layer with fewer dislocations than the initial surface, thereby enhancing the performance of semiconductor devices.
Implementation Method 1
growing an intermediate layer with enhanced surface indentations and promoting the intersection of dislocations, followed by lateral growth over the agglomerated dislocations
Data Source
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.