GaN Underlayer Gap Elimination via Seed Layer Growth
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Solution Overview
Problem
Existing methods for forming a GaN-based compound semiconductor underlayer on a sapphire substrate result in gaps between the underlayer and the substrate, leading to instability and inefficient light extraction in GaN-based semiconductor light-emitting elements, as light paths through the underlayer and substrate are problematic.
Innovation Solution
A method involving the formation of a strip seed layer and a crystal growth promoting layer on a sapphire substrate, followed by epitaxial growth of the underlayer from these layers, ensuring continuous coverage and eliminating gaps between the underlayer and the substrate, with optional subsequent mask layer formation and selective removal for repeated growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epitaxial growth is performed directly on the sapphire substrate without intermediate layers, then the growth process is simple, but gaps form between the underlayer and substrate leading to dislocation defects and poor light extraction
Solution Approach 1:
The patent applies preliminary action by forming a crystal growth promoting layer on the sapphire substrate before epitaxial growth of the underlayer. This intermediate layer is prepared in advance to ensure complete coverage and prevent gap formation during subsequent growth, thereby eliminating dislocation defects and improving structural integrity without significantly complicating the overall process
Solution Approach 2:
The crystal growth promoting layer serves as an intermediary between the sapphire substrate and the GaN-based underlayer. This intermediate layer mediates the interface between substrate and underlayer, ensuring continuous coverage, preventing gap formation, and eliminating dislocation defects that would otherwise propagate through the structure
2Use of energy by moving object
If gaps exist between the underlayer and sapphire substrate, then the growth process is simpler with fewer steps, but light extraction efficiency deteriorates due to problematic light paths
Solution Approach 1:
The crystal growth promoting layer is formed in advance on the sapphire substrate to ensure continuous coverage before underlayer growth. This preliminary action prevents gap formation that would create problematic light paths, thereby improving light extraction efficiency while maintaining uniform underlayer coverage
Solution Approach 2:
The crystal growth promoting layer acts as an intermediary that ensures continuous interface coverage between substrate and underlayer. This eliminates gaps that would create problematic light paths, thereby improving light extraction efficiency while maintaining manufacturing precision
3Manufacturing precision
If multiple growth steps with mask layers are used to achieve complete coverage, then uniformity improves, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The crystal growth promoting layer is formed in advance to provide a uniform foundation for underlayer growth. This preliminary action ensures complete and uniform coverage in a single growth step, eliminating the need for multiple iterative growth steps with mask layers, thereby maintaining high uniformity while improving productivity
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 prevents dislocation defects and ensures a high-quality GaN-based semiconductor light-emitting element with improved light extraction efficiency by eliminating gaps and promoting uniform crystal growth, enhancing the structural integrity and performance of the underlayer.
Implementation Method 1
various studies have been conducted on methods to grow a GaN-based compound semiconductor layer on a sapphire substrate in a lateral direction (hereinafter, the methods will be referred to as epitaxial growth in a lateral direction or epitaxial lateral overgrowth (ELO))
Implementation Method 2
a GaN-based compound semiconductor layer is laterally grown from the seed layers
Data Source
AI summary
A method for forming an underlayer composed of a GaN-based compound semiconductor is provided. In this method, at the time of epitaxial growth of an underlayer on the surface of a sapphire substrate, no gap is generated between the underlayer and the surface of the sapphire substrate. The method for forming an underlayer composed of a GaN-based compound semiconductor includes the steps of forming strip seed layers composed of a GaN-based compound semiconductor on the surface of a sapphire substrate, forming a crystal growth promoting layer composed of a GaN-based compound semiconductor on the top surfaces and both the side surfaces of the seed layers, and on the exposed surfaces of the sapphire substrate, and epitaxially growing an underlayer composed of a GaN-based compound semiconductor from the parts of the crystal growth promoting layer.