InGaN Buffer Layer for Group III Nitride Light Emitting Devices
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Solution Overview
Problem
The challenge lies in producing group III nitride semiconductor light emitting devices with favorable crystallinity and productivity, as existing methods face issues with lattice mismatch, threading dislocations, and limited improvements in crystallinity due to amorphous and polycrystalline phases in buffer layers, and differences in lattice constants between buffer and gallium nitride layers.
Innovation Solution
A method involving the formation of a buffer layer with a composition of AlXGa1-XN (0≦X<1) by activating a metallic Ga source and a gas containing a group V element using plasma, followed by the sequential lamination of n-type and p-type semiconductor layers, where the buffer layer is formed using reactive sputtering methods to achieve favorable orientation and prevent substrate reaction with source gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a low temperature buffer layer composed of AlN or AlGaN is first laminated on the substrate to grow crystals of group III nitride semiconductor, then the crystallinity of the grown crystals is improved, but threading dislocations are incorporated inside the grown crystals due to lattice mismatch
Solution Approach 1:
The patent changes the composition parameter of the buffer layer from conventional AlN or AlGaN to InGaN with specific indium content (0.05≤x≤0.5 in InxGa1-xN). This parameter change allows the buffer layer to have a lattice constant closer to GaN, reducing lattice mismatch and threading dislocations while maintaining improved crystallinity.
Solution Approach 2:
The patent uses a composite buffer layer structure consisting of InxGa1-xN buffer layer in combination with AlN or AlGaN buffer layer. This composite approach leverages the lattice-matching capability of InGaN while utilizing the protective and structural benefits of AlN/AlGaN, achieving both reduced dislocations and improved crystallinity.
2Object-affected harmful factors
If a buffer layer is formed on a substrate by a method other than MOCVD method (such as reactive sputtering) to prevent substrate reaction with source materials, then substrate reaction is prevented, but the buffer layer may contain amorphous and polycrystalline phases which limit further improvement in crystallinity
Solution Approach 1:
The patent replaces the reactive sputtering method with MOCVD method for forming the buffer layer. This substitution eliminates the substrate reaction problem that occurs with sputtering while enabling the formation of high-quality single-crystal buffer layers with excellent crystallinity, avoiding the amorphous and polycrystalline phase limitations.
3Productivity
If crystals of group III nitride semiconductor are grown on a sapphire or SiC substrate by MOCVD method, then the productivity is improved, but there is a large lattice mismatch (16% for sapphire, 6% for SiC) which makes it difficult to grow crystals with satisfactory crystallinity
Solution Approach 1:
The patent introduces an InxGa1-xN buffer layer as an intermediary between the sapphire/SiC substrate and the GaN crystal layer. This intermediary buffer layer has a lattice constant that bridges the gap between the substrate and GaN, reducing the effective lattice mismatch and enabling high-quality crystal growth while maintaining the productivity benefits of MOCVD method on commercially available substrates.
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 enables the growth of group III nitride semiconductors with excellent crystallinity and light emitting properties, improving productivity and preventing substrate reactions, resulting in high-quality light emitting devices.
Implementation Method 1
activating a metallic Ga source and a gas containing a group V element using plasma
Implementation Method 2
the buffer layer is formed using reactive sputtering methods
Data Source
AI summary
Provided is a method for producing a group III nitride semiconductor light emitting device capable of producing a group III nitride semiconductor light emitting device with excellent light emitting properties with excellent productivity; a group III nitride semiconductor light emitting device; and a lamp.Provided is a method in which a buffer layer 12 composed of a group III nitride compound is laminated on a substrate 11 and then an n-type semiconductor layer 14 provided with an underlying layer 14a, a light emitting layer 15, and an p-type semiconductor layer 16 are sequentially laminated on the buffer layer 12, and is a method in which the buffer layer 12 is formed so as to have a composition of AlXGa1-XN (0≦X<1) by activating, with plasma, and thereby reacting at least a metallic Ga source and a gas containing a group V element, and the underlying layer 14 is formed on the buffer layer 12.