Epitaxial Structure Defect Termination Blocks
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Solution Overview
Problem
In gallium nitride-based light-emitting devices, lattice mismatch between substrates and epitaxial layers leads to dislocation formation, reducing light emitting efficiency, and existing methods to mitigate defects are either inefficient or increase epitaxial layers, which can decrease yield and quantum efficiency.
Innovation Solution
An epitaxial structure with a base layer, a first epitaxial layer having concentrated defect groups and recesses, and defect-termination blocks made of a different material, which are polished to create a planarized crystal growth surface, effectively terminating defects and reducing defect density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple epitaxial layers are added to reduce defects, then defect density in the active layer decreases, but yield decreases and quantum efficiency improvement attenuates
Solution Approach 1:
The patent extracts and removes defect-prone regions by forming recesses at locations where dislocations concentrate in the first epitaxial layer. By selectively removing material at these defect locations and filling with defect-termination blocks, the harmful dislocations are extracted from the growth path, allowing subsequent epitaxial layers to grow with reduced defect density without requiring excessive layer stacking.
Solution Approach 2:
The patent performs preliminary defect management by forming recesses and filling them with defect-termination blocks before growing the second epitaxial layer. This preliminary action terminates defect propagation at the interface, creating a clean growth surface for subsequent layers and eliminating the need for multiple thick epitaxial layers to achieve defect reduction.
2Ease of manufacture
If reactive ion etching is used to remove coated film, then film removal is achieved, but defects increase due to etching processes
Solution Approach 1:
The patent introduces an intermediary material (defect-termination blocks made of material different from the first epitaxial layer) that serves as a mediator between the etching process and the epitaxial layer. This intermediary material can be selectively removed or modified without damaging the underlying epitaxial structure, allowing film removal while protecting against defect generation.
Solution Approach 2:
The patent changes the material parameters of the defect-termination blocks to have different etch resistance or removal characteristics compared to the first epitaxial layer. This parameter change allows selective removal of the coated film and defect-termination blocks using controlled etching processes that do not generate excessive defects in the sensitive epitaxial regions.
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 epitaxial structure achieves a low defect density, enhancing light emitting efficiency and quantum efficiency while maintaining a high yield by effectively terminating defects and providing a suitable substrate for semiconductor devices.
Implementation Method 1
a plurality of defect-termination blocks respectively and filling the first recesses and having polished surfaces
Data Source
AI summary
An epitaxial structure having a low defect density includes: a base layer; a first epitaxial layer having a plurality of concentrated defect groups, and an epitaxial surface that has a plurality of first recesses corresponding in position to the concentrated defect groups, the sizes of the first recesses being close to each other; and a plurality of defect-termination blocks respectively and filling the first recesses and having polished surfaces. The defect-termination blocks are made of a material which is different in removal rate from that of the first epitaxial layer. The polished surfaces are substantially flush with the epitaxial surface so that the first epitaxial layer has a substantially planarized crystal growth surface