Nitride Crystal Growth on Silicon via Amorphous Oxide Buffer
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Solution Overview
Problem
The challenge lies in growing high-quality nitride single crystals on silicon substrates due to lattice constant and thermal expansion coefficient mismatches, leading to defects and cracks, which hinder the commercialization of nitride semiconductor light emitting devices.
Innovation Solution
A novel buffer structure is introduced, comprising a silicon substrate with a first nitride buffer layer, an amorphous oxide film, and a second nitride buffer layer, where the amorphous oxide film blocks dislocations and enables the growth of a high-quality nitride single crystal using Hydride Vapor Phase Epitaxy (HVPE).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon substrate is used to grow nitride single crystal, then manufacturing cost is reduced and mass production is enabled, but lattice constant and thermal expansion coefficient mismatches cause defects and cracks in the GaN layer
Solution Approach 1:
An amorphous alumina film is introduced as an intermediary layer between the silicon substrate and the nitride buffer layer. This intermediate layer acts as a mediator that blocks dislocation propagation from the silicon substrate while allowing the nitride crystal to grow with reduced defect density, thus resolving the contradiction between using cheap silicon substrates and maintaining high crystal quality
Solution Approach 2:
The patent employs a composite buffer structure consisting of multiple nitride buffer layers with different aluminum compositions (AlN, AlGaN) combined with an amorphous alumina film. This composite structure leverages the properties of different materials to simultaneously achieve lattice matching, thermal expansion compensation, and dislocation blocking, enabling high-quality GaN growth on silicon substrates
2Reliability
If conventional buffer structures (AlN buffer layer alone or with AlGaN intermediate layer) are used, then some defect reduction is achieved, but cracks still occur due to unresolved lattice and thermal expansion mismatches
Solution Approach 1:
The amorphous alumina film serves as a specialized intermediary that conventional buffer structures lack. It specifically blocks dislocation propagation while the graded AlGaN layer handles lattice matching, creating a division of functions that more effectively resolves the underlying mismatch problems without excessive complexity
3Manufacturing precision
If sapphire or SiC substrates are used, then high-quality nitride single crystal growth is achieved, but manufacturing cost increases and substrate size is limited to 2 or 3 inches
Solution Approach 1:
The patent replaces expensive, size-limited sapphire or SiC substrates with inexpensive silicon substrates that can be grown in large sizes. The silicon substrate, while having mismatch issues, becomes viable through the use of the amorphous alumina film and optimized buffer structure, effectively using a 'cheap' substrate alternative that enables mass production
Solution Approach 2:
The amorphous alumina film acts as a mediator that enables the use of silicon substrates by blocking dislocation propagation, thereby achieving crystal quality comparable to expensive substrates while benefiting from the cost and size advantages of silicon
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 method reduces dislocation density and allows for the growth of high-quality nitride single crystals on silicon substrates, enhancing the performance and longevity of nitride semiconductor light emitting devices, making them suitable for commercial production without the need for expensive sapphire or SiC substrates.
Implementation Method 1
the amorphous oxide film blocks dislocations and enables the growth of a high-quality nitride single crystal
Implementation Method 2
a novel buffer structure is introduced, comprising a silicon substrate with a first nitride buffer layer, an amorphous oxide film, and a second nitride buffer layer, where the amorphous oxide film blocks dislocations and enables the growth of a high-quality nitride single crystal using Hydride Vapor Phase Epitaxy (HVPE)
Data Source
AI summary
The invention provides a method for growing a nitride single crystal on a silicon wafer and a method for manufacturing a light emitting device using the same. In growing the nitride single crystal according to one aspect of the invention, first, a silicon substrate having a surface in (111) crystal orientation is prepared. A first nitride buffer layer is formed on the surface of the silicon substrate. Then, an amorphous oxide film is disposed on the first nitride buffer layer. A second buffer layer is disposed on the amorphous oxide film. Thereafter, the nitride single crystal is formed on the second nitride buffer layer.