AlGaN Substrate Growth via MOCVD Parameter Optimization
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Solution Overview
Problem
Current methods for fabricating AlxGa1-xN substrates face challenges in achieving high-quality crystallinity and low dislocation density, especially for ultraviolet and deep-ultraviolet light-emitting devices, due to light absorption and crack formation issues in GaN substrates, and limitations in depositing thick layers with high precision and speed using existing vapor phase growth methods.
Innovation Solution
The MOCVD method is used to deposit a layer of AlxGa1-xN with a high growth speed of 5 μm/hour on a base material, such as sapphire, SiC, Si, ZnO, or Ga2O3, followed by removal of the base material, allowing for the production of a self-independent substrate with controlled composition and enhanced crystallinity, thereby reducing light absorption and crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the MOCVD method is used to deposit AlxGa1-xN layer with high growth speed, then productivity is improved, but manufacturing precision deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the V/III ratio to 1000 or less and setting the growth temperature to 1200°C or higher. These parameter adjustments enable high-growth-speed deposition while maintaining precise compositional control of the AlxGa1-xN layer, resolving the contradiction between productivity and manufacturing precision.
2Reliability
If a thick layer of AlxGa1-xN is deposited to form a self-independent substrate, then reliability is improved, but productivity deteriorates
Solution Approach 1:
By changing the growth parameters to V/III ratio of 1000 or less and temperature of 1200°C or higher, the patent achieves both thick layer deposition and high growth speed. This enables formation of self-independent substrates with reliable thickness while maintaining high productivity through accelerated growth rates.
3Reliability
If GaN substrate is used to reduce dislocation density, then reliability is improved, but light absorption increases
Solution Approach 1:
The patent applies local quality by creating an AlxGa1-xN substrate with controlled aluminum composition that balances crystallinity and optical properties. The specific compositional control allows the substrate to provide necessary structural quality while minimizing light absorption in the ultraviolet and deep-ultraviolet regions, resolving the contradiction between reliability and harmful light absorption.
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 results in a substrate that significantly enhances luminous efficiency and reduces dislocation density, enabling the fabrication of high-output light-emitting devices capable of emitting light in the ultraviolet and deep-ultraviolet regions with improved mechanical strength and optical characteristics.
Implementation Method 1
The MOCVD method that is a vapor phase growth method similar to the HVPE method has a feature capable of controlling the composition of a mixed crystal of AlN and GaN with higher precision than the HVPE method
Implementation Method 2
a crystal has been deposited on a processed substrate or a processed under layer in order to enhance the crystallinity of the under layer, thereby reducing the dislocation
Data Source
AI summary
A substrate is formed of AlxGa1-xN, wherein 0<x≦̸1. The substrate is a single crystal and is used producing a Group III nitride semiconductor device. A method for producing a substrate of AlxGa1-xN, wherein 0<x≦̸1, includes the steps of forming a layer of AlxGa1-xN, wherein 0<x≦̸1, on a base material and removing the base material. The method adopts the MOCVD method using a raw material molar ratio of a Group V element to Group III element that is 1000 or less, a temperature of 1200° C. or more for forming the layer of AlxGa1-xN, wherein 0<x≦̸1. The base material is formed of one member selected from the group consisting of sapphire, SiC, Si, ZnO and Ga2O3. The substrate is used for fabricating a Group III nitride semiconductor device.