Scandium Nitride Buffer Layer for High-Temperature AlGaN Growth
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Solution Overview
Problem
Conventional Group III nitride semiconductor growth on sapphire substrates faces challenges due to lattice constant differences, leading to poor crystal quality and limited high-temperature processing capabilities, especially for AlxGa1-xN layers with high Al composition, which restricts the wavelength range and efficiency of light-emitting diodes.
Innovation Solution
A Group III nitride semiconductor growth substrate with a scandium nitride film formed on a crystal growth substrate, allowing for chemical lift-off without reducing crystallinity, using a Sc metal layer nitrided in an ammonia gas mixture, and optionally incorporating AlxGa1-xN buffer layers for improved crystallinity and high-temperature compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a CrN layer is used as a buffer layer for growing AlxGa1-xN with high Al composition, then the dislocation density is reduced and crystal quality is improved, but the CrN layer melts at high growth temperatures (>1050°C) making chemical lift-off difficult
Solution Approach 1:
The patent changes the material parameter from CrN to ScN buffer layer. ScN has a melting point exceeding 2000°C, which is significantly higher than CrN's 1050°C melting point. This parameter change allows the buffer layer to withstand high growth temperatures (>1050°C) for AlxGa1-xN with high Al composition while maintaining structural integrity for chemical lift-off processes.
2Manufacturing precision
If a sapphire substrate is used for growing Group III nitride semiconductor, then the lattice constant mismatch is reduced with a buffer layer, but the substrate cannot dissipate heat effectively due to low thermal conductivity
Solution Approach 1:
The patent introduces a ScN buffer layer as an intermediary between the sapphire substrate and the AlxGa1-xN layer. This intermediary layer serves dual purposes: it reduces lattice constant mismatch to improve crystal quality, and it enables effective heat dissipation pathways while maintaining the benefits of the sapphire substrate platform.
3Ease of operation
If a sapphire substrate is used with n-electrode and p-electrode formed on one surface, then the structure can flow electric current, but high electric current cannot flow and little heat is dissipated
Solution Approach 1:
The patent segments the substrate system by introducing a ScN buffer layer that enables thermal management, allowing the device to achieve high power output capabilities while maintaining electrical current flow through the structured electrode configuration on the sapphire substrate.
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
Enables the production of Group III nitride semiconductor substrates and elements with good crystallinity, covering a broader wavelength range and high-temperature growth conditions, facilitating efficient chemical lift-off and reducing manufacturing costs by using non-corrosive acid etchants.
Implementation Method 1
using a Sc metal layer nitrided in an ammonia gas mixture
Implementation Method 2
facilitating efficient chemical lift-off and reducing manufacturing costs by using non-corrosive acid etchants
Data Source
AI summary
An object of the present invention is to provide a Group III nitride semiconductor epitaxial substrate, a Group III nitride semiconductor element, and a Group III nitride semiconductor free-standing substrate, which have good crystallinity, with not only AlGaN, GaN, and GaInN the growth temperature of which is 1050° C. or less, but also with AlxGa1-xN having a high Al composition, the growth temperature of which is high; a Group III nitride semiconductor growth substrate used for producing these, and a method for efficiently producing those. The present invention provides a Group III nitride semiconductor growth substrate comprising a crystal growth substrate including a surface portion composed of a Group III nitride semiconductor which contains at least Al, and a scandium nitride film formed on the surface portion are provided.