Nitride Semiconductor Substrate with Multifunctional Seed Layer
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Solution Overview
Problem
Current methods for growing single-crystal nitride-based semiconductor substrates face challenges such as mechanical and thermal strain, decomposition, and inefficient heat dissipation on substrates like sapphire and silicon carbide, leading to poor quality and high operational costs, while substrates like zinc oxide are unstable at high temperatures and have lattice constant differences with nitride-based semiconductors.
Innovation Solution
A method involving the sequential formation of a seed material layer and a multifunctional substrate on a first substrate, using materials like aluminum oxide, aluminum nitride, and gallium nitride, which provides thermal stability and reduces dislocation density, allowing for high-quality single-crystal nitride-based semiconductor growth under high-temperature hydrogen atmospheres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a thick insulating sapphire substrate is used, then mechanical stability is improved, but heat dissipation capability deteriorates
Solution Approach 1:
The substrate system is segmented into multiple functional layers: a thick sapphire substrate for mechanical stability, a thin multifunctional substrate layer (20-200 nm) for heat dissipation and crystal growth, and a nitride-based semiconductor layer for device functionality. This segmentation allows each layer to perform its optimal function without compromising the others.
Solution Approach 2:
The invention uses a composite substrate structure combining sapphire (Al2O3) with a multifunctional substrate material such as aluminum nitride (AlN), gallium nitride (GaN), or zinc oxide (ZnO). This composite structure integrates the mechanical stability of sapphire with the superior thermal conductivity of the multifunctional material, resolving the heat dissipation problem while maintaining structural integrity.
2Loss of energy
If zinc oxide substrate is used, then cost and thermal conductivity are improved, but stability at high temperature deteriorates
Solution Approach 1:
The invention creates a composite structure where zinc oxide or other multifunctional materials are combined with sapphire or aluminum nitride layers. This composite approach allows the system to achieve high thermal conductivity from the zinc oxide while the sapphire or aluminum nitride provides thermal stability at high temperatures, preventing decomposition.
Solution Approach 2:
The multifunctional substrate layer acts as an intermediary between the sapphire substrate and the nitride-based semiconductor layer. It provides a stable interface that prevents direct thermal degradation of the zinc oxide or other temperature-sensitive materials while maintaining thermal conductivity for heat dissipation.
3Ease of manufacture
If conventional substrates are used, then manufacturing process is simplified, but dislocation density increases
Solution Approach 1:
The multifunctional substrate layer serves as an intermediary buffer layer between the conventional sapphire substrate and the nitride-based semiconductor layer. This intermediate layer accommodates lattice mismatch and reduces dislocation propagation, achieving low dislocation density (1×10^8 to 1×10^10 cm^-2) while still using conventional, easy-to-manufacture sapphire substrates.
Solution Approach 2:
The invention changes the structural parameters of the substrate system by introducing a thin multifunctional layer with specific thickness (20-200 nm) and material composition. This parameter change transforms the substrate from a simple single-layer structure to a multi-layer structure that optimizes both manufacturing ease and crystal quality.
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 production of high-quality nitride-based light emitting devices with superior light efficiency and heat dissipation, suitable for next-generation white light sources, while operating at low voltages and improving product yield.
Implementation Method 1
the transparent conductive zinc oxide (ZnO) substrate has a small difference in a lattice constant relative to the nitride-based semiconductor
Implementation Method 2
these conductive substrates also represent problems at a temperature of 500° C. or more due to the motion of the dislocation slip system provided in the conductive substrates, thereby causing strain to and decomposition of materials
Implementation Method 3
the transparent ZnO substrate has been recently spotlighted as a next-generation substrate for the nitride-based light emitting devices... representing superior electrical and thermal conductivities
Implementation Method 4
the surface of the transparent conductive zinc oxide (ZnO) substrate becomes unstable under a high temperature of 600° C. or more and a high vacuum of 10−3 torr or more, thus easily decomposing the materials of the transparent conductive zinc oxide (ZnO) substrate. In addition, reduction of the transparent conductive ZnO substrate is promoted in reducing ambient employment of ammonium (NH3) and hydrogen (H2)
Implementation Method 5
single-crystal nitride-based semiconductors have become very important materials in optical industrial fields. In general, optoelectronic devices employing the single-crystal nitride-based semiconductors are grown from the upper surface of a thick insulating sapphire substrate or a conductive silicon carbide (SiC) substrate under the hydrogen atmosphere where ammonium (NH3) and hydrogen (H2) carrier gas are provided in a high temperature condition of 1200° C. or more
Data Source
AI summary
A nitride-based light emitting device is manufactured by using a single-crystal nitride-based semiconductor substrate. A seed material layer is deposited on a first substrate where organic residues including a natural oxide layer are removed from an upper surface of the first substrate. A multifunctional substrate is grown from the seed material layer. The single-crystal nitride-based semiconductor layer including a nitride-based buffer layer is formed on the multifunctional substrate. The seed material layer primarily assists the growth of the multifunctional substrate, which is essentially required for the growth of the single-crystal nitride-based semiconductor substrate. The multifunctional substrate is prepared in the form of a single-crystal layer or a poly-crystal layer having a hexagonal crystalline structure. The light emitting device employing the single-crystal nitride-based semiconductor substrate is used as a next-generation white light source having high capacity, large area, high brightness and high performance.