Gallium Oxide Laminated Structure for Low-Defect Crystalline Films
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Solution Overview
Problem
Crystalline oxide films containing gallium oxide, such as α-Ga2O3, used in power semiconductors face challenges with high crystal defects and domain formation due to their metastable phase and low deposition temperature, affecting breakdown electric field properties.
Innovation Solution
A laminated structure with a crystalline oxide film having a base substrate and a crystalline oxide film containing gallium oxide as a main component, where the film has an average reflectance of light with a wavelength of 400 to 800 nm of 16% or greater, formed using Mist CVD with a nozzle temperature higher than room temperature, resulting in extremely few crystal defects and excellent crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heteroepitaxial growth is used to form α-Ga2O3 film on sapphire substrate, then the film can be formed, but crystal defects increase due to lattice constant mismatch
Solution Approach 1:
A buffer layer comprising (AlxGa1-x)2O3 is introduced between the sapphire substrate and the α-Ga2O3 semiconductor layer. This buffer layer acts as an intermediary that gradually transitions the lattice structure, reducing the abrupt mismatch between sapphire and α-Ga2O3. The buffer layer composition is controlled with 0.05 ≤ x ≤ 0.45, creating a graded structure that minimizes dislocation density and crystal defects while enabling successful heteroepitaxial growth.
2Stability of the object's composition
If low deposition temperature is used for α-Ga2O3 film formation, then the metastable phase can be maintained, but domain formation increases reducing crystallinity
Solution Approach 1:
The invention optimizes the buffer layer composition parameter x in (AlxGa1-x)2O3 to control the deposition temperature and crystallinity. By controlling 0.05 ≤ x ≤ 0.45, the buffer layer enables deposition at temperatures that maintain the metastable α-phase while improving crystallinity. The composition parameter x directly influences the deposition temperature and crystal structure quality, allowing simultaneous achievement of phase stability and high crystallinity.
Solution Approach 2:
The invention uses a composite structure consisting of sapphire substrate, (AlxGa1-x)2O3 buffer layer, and α-Ga2O3 semiconductor layer. This composite material system allows the buffer layer to mediate between the substrate and the semiconductor layer, providing thermal and structural benefits that enable low-temperature deposition while maintaining high crystallinity and preventing domain formation.
3Manufacturing precision
If buffer layer is introduced to reduce crystal defects, then dislocation density decreases, but domain formation may still occur
Solution Approach 1:
The invention precisely controls the buffer layer composition parameter x (0.05 ≤ x ≤ 0.45) to simultaneously achieve low dislocation density and prevent domain formation. This parameter optimization ensures that the buffer layer not only reduces crystal defects but also promotes uniform crystal growth, eliminating mosaic structure formation and ensuring high breakdown electric field properties necessary for power semiconductor applications.
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 approach achieves a crystalline oxide film with improved crystallinity and semiconductor properties, including high breakdown voltage, by reducing crystal defects and preventing domain formation in the semiconductor device.
Implementation Method 1
a method of forming a crystalline oxide film containing gallium oxide as a main component by Mist CVD
Implementation Method 2
the film is formed with temperature of the nozzle or an inner wall of the deposition chamber higher than a room temperature
Data Source
AI summary
A laminated structure having at least a base substrate and a crystalline oxide film containing gallium oxide as a main component, wherein an average value of reflectance of light having a wavelength of 400 to 800 nm is 16% or greater on a surface on a side of the crystalline oxide film of the laminated structure. Thus, the invention provides a laminated structure having a crystalline oxide film containing gallium oxide as a main component with extremely few crystal defects, excellent crystallinity, and excellent semiconductor properties when applied to a semiconductor device.