GaN Semiconductor Buffer Layer Orientation Control
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Solution Overview
Problem
Conventional low-temperature-deposited buffer layers on sapphire substrates for gallium-nitride-based semiconductor devices fail to achieve consistent and unified orientation, leading to suboptimal single-crystal characteristics in GaN-based semiconductor layers.
Innovation Solution
A low-temperature-deposited buffer layer composed of AlXGaYN (0.5<Y≦1, X+Y=1) with a predominant amount of gallium is formed on a sapphire substrate, having a single-crystal structure with a specific orientation parallel to the substrate's basal plane, and further enhanced with a thin-film layer or superlattice structure to promote well-unified orientation of the GaN-based semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-temperature-deposited buffer layer is formed on a sapphire substrate to mitigate lattice constant mismatch, then the formation of GaN-based semiconductor layers becomes feasible, but the orientation of the single-crystal layer is not sufficiently unified, leading to poor single-crystal characteristics
Solution Approach 1:
The patent changes the compositional parameters of the buffer layer by using AlXGaYN with Y>0.5 (gallium-rich composition) instead of conventional stoichiometric compositions. This parameter change promotes the formation of a single-crystal layer with unified orientation at low deposition temperatures, thereby improving both single-crystal characteristics and orientation uniformity simultaneously
Solution Approach 2:
The patent employs a composite buffer layer structure consisting of AlXGaYN mixed crystal with specific composition ratios. This composite material approach allows the buffer layer to simultaneously provide lattice mismatch mitigation and promote unified crystal orientation, resolving the contradiction between reliability and manufacturing precision
2Ease of manufacture
If a low-temperature-deposited buffer layer is used to enable GaN layer formation on sapphire substrates, then device fabrication becomes possible, but consistent formation of GaN layers with well-unified orientation cannot be achieved
Solution Approach 1:
By changing the compositional parameters to gallium-rich AlXGaYN (Y>0.5), the patent maintains low-temperature deposition feasibility while simultaneously achieving consistent orientation of GaN layers. This parameter modification allows the buffer layer to guide crystal growth in a unified direction without requiring high deposition temperatures
3Temperature
If conventional buffer layers are formed at low temperature to mitigate lattice mismatch, then the buffer layer can be deposited on sapphire substrates, but the single-crystal layer orientation remains insufficiently unified
Solution Approach 1:
The patent changes the compositional parameters of the buffer layer material to gallium-rich AlXGaYN (Y>0.5), which enables unified crystal orientation to be achieved at low deposition temperatures. This compositional parameter change fundamentally alters the growth characteristics, allowing low-temperature deposition without sacrificing orientation precision
Solution Approach 2:
The use of composite AlXGaYN material with specific composition ratios creates a buffer layer that simultaneously provides low-temperature depositability and promotes unified crystal orientation. The composite nature of the material allows it to exhibit dual functionality that resolves the contradiction between temperature and orientation precision
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 GaN-based semiconductor layer with excellent single-crystal characteristics and improved orientation, leading to enhanced performance in semiconductor devices such as light-emitting diodes with reduced local breakdowns and improved emission characteristics.
Implementation Method 1
a low-temperature-deposited buffer layer which is composed of a Group III nitride material of AlXGaYN (0.5<Y≦1, X+Y=1), has a single crystal in an as-grown state joined to a (0001) plane of the sapphire substrate
Data Source
AI summary
A gallium-nitride-based semiconductor stacked structure includes a sapphire substrate; a low-temperature-deposited buffer layer which is composed of a Group III nitride material of AlXGaYN (0.5<Y≦1, X+Y=1) containing gallium (Ga) in a predominant amount with respect to aluminum (Al), which has been grown at low temperature and which is provided in a junction area thereof joined to a (0001) plane (c-plane) of the sapphire substrate with a single crystal in an as-grown state; and a gallium-nitride (GaN)-based semiconductor layer formed on the low-temperature-deposited buffer layer. The low-temperature-deposited buffer layer is predominantly composed of an as-grown single crystal which has a [1.0.−1.0.] orientation parallel to a [2.−1.−1.0.] direction of a lattice forming a (0001) basal plane of the sapphire substrate.