Thin Buffer Layer for Oriented Nanowire Growth
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Solution Overview
Problem
Existing nanowire-based devices face challenges with substrate bowing and high defect densities due to thick epitaxial buffer layers, which limit large-scale processing and increase costs, especially in nitride semiconductor devices like LEDs, where high thermal uniformity and crystalline quality are crucial.
Innovation Solution
A substrate with a bulk layer and a buffer layer of less than 2 μm thickness, allowing for nanowire growth without the need for costly and time-consuming epitaxy, using materials with higher defect and dislocation densities, and enabling the use of lower-quality substrates like Si (111) and amorphous substrates, while reducing substrate bowing and allowing for integrated electronic connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thick epitaxial buffer layers are used to compensate for lattice mismatch, then crystalline quality is improved, but substrate bowing increases and manufacturing cost increases
Solution Approach 1:
The invention changes the thickness parameter of the buffer layer from conventional thick layers (several μm) to a thin layer (less than 2 μm, preferably 0.1-1 μm). This parameter change resolves the contradiction by providing sufficient strain compensation while minimizing substrate bowing, enabling large-scale processing without the harmful effects of thick buffer layers.
Solution Approach 2:
The invention uses cheaper substrate materials (Si, SiC, sapphire) that can have higher defect densities, replacing the need for expensive high-quality epitaxial substrates. The thin buffer layer serves as a disposable intermediate layer that compensates for mismatches without requiring the substrate itself to be of ultra-high quality, thus reducing overall manufacturing cost.
2Manufacturing precision
If thick epitaxial buffer layers are used to compensate for lattice mismatch, then crystalline quality is improved, but manufacturing cost increases
Solution Approach 1:
The invention uses cheaper substrate materials (Si, SiC, sapphire) that can have higher defect densities, replacing the need for expensive high-quality epitaxial substrates. The thin buffer layer serves as a disposable intermediate layer that compensates for mismatches without requiring the substrate itself to be of ultra-high quality, thus reducing overall manufacturing cost.
Solution Approach 2:
The invention changes the thickness parameter of the buffer layer from conventional thick layers (several μm) to a thin layer (less than 2 μm, preferably 0.1-1 μm). This parameter change resolves the contradiction by providing sufficient strain compensation while minimizing substrate bowing, enabling large-scale processing without the harmful effects of thick buffer layers.
3Stability of the object's composition
If conventional buffer layers are used, then strain compensation is achieved, but thermal uniformity deteriorates
Solution Approach 1:
The invention changes the thickness parameter of the buffer layer from conventional thick layers to a thin layer (less than 2 μm). This parameter change resolves the contradiction by providing sufficient strain compensation through the thin layer while minimizing its impact on thermal uniformity, as thinner layers have less effect on heat distribution during nanowire growth.
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 high-quality nanowires with reduced substrate curvature, increased material choices, and the ability to use cheaper substrates, while avoiding costly epitaxy steps, thus facilitating large-area wafer production and improving device performance.
Implementation Method 1
mismatch between substrate and the nitride semiconductors, for example lattice mismatch, introduce detrimental defects such as cracks in the grown material. In prior art, dislocations have been suppressed by using epitaxial substrates or substrates with an epitaxial buffer layer.
Implementation Method 2
several μm thick buffer layers are epitaxially grown on the substrates in order to function as a strain accommodating layers and a high quality epitaxial foundation to grow the device on
Implementation Method 3
The thickness of the buffer layer that is deposited on the substrate is less than 2 μm... This approach enables the growth of high-quality nanowires with reduced substrate curvature
Data Source
AI summary
The present invention provides a substrate (1) with a bulk layer (3) and a buffer layer (4) having a thickness of less than 2 μm arranged on the bulk layer (3) for growth of a multitude of nanowires (2) oriented in the same direction on a surface (5) of the buffer layer (4). A nanowire structure, a nanowire light emitting diode comprising the substrate (1) and a production method for fabricating the nanowire structure is also provided. The production method utilizes non-epitaxial methods for forming the buffer layer (4).