A-Plane Group III Nitride Semiconductor on R-Plane Sapphire
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Solution Overview
Problem
The challenge lies in growing high-quality A-plane group III nitride semiconductor layers on R-plane sapphire substrates, which are susceptible to surface pits and require complex epitaxial lateral overgrowth or additional zinc oxide layers, leading to increased costs and inefficiencies, especially for green LEDs with low external quantum efficiency.
Innovation Solution
A method involving a buffer layer of aluminum gallium nitride and an underlying A-plane group III nitride semiconductor layer grown in stages with controlled substrate temperatures, achieving a pit density of 1×10^10 cm^-2 or less and a film thickness of 20 μm or less, using MOCVD and incorporating island-like or columnar crystalline structures to enhance surface flatness and crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If R-plane sapphire substrate is used for growing group III nitride semiconductor layers, then production cost is reduced, but surface pits form and crystallinity deteriorates
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the R-plane sapphire substrate and the group III nitride semiconductor layer. This buffer layer mediates the lattice mismatch and surface quality issues, enabling high-quality semiconductor growth on the cost-effective R-plane substrate without direct contact between the semiconductor and problematic substrate surface
Solution Approach 2:
The patent applies preliminary surface treatment and buffer layer deposition before growing the main semiconductor layer. By preparing the substrate surface in advance with appropriate buffer layers, the method prevents surface pit formation and ensures good crystallinity in the final semiconductor layer
2Ease of manufacture
If R-plane sapphire substrate is used, then production cost is reduced, but additional complex processes (epitaxial lateral overgrowth or zinc oxide layers) are required
Solution Approach 1:
The patent optimizes growth parameters such as temperature, pressure, and gas flow ratios during MOCVD processing. By carefully controlling these parameters, the method achieves high-quality semiconductor layers on R-plane substrates using a simplified single-step process rather than multiple complex processes
Solution Approach 2:
The patent employs composite buffer layer structures with different materials (such as AlN, AlGaN) having progressively better lattice matching with the semiconductor layer. This composite approach provides gradual transition from the sapphire substrate to the semiconductor, reducing dislocation density without requiring complex additional processes
3Ease of manufacture
If conventional growth methods are used on R-plane sapphire, then production cost is reduced, but green LED efficiency remains low
Solution Approach 1:
The patent creates local quality improvements by forming buffer layers with specific crystal orientations and compositions in different regions of the growth process. This ensures that the semiconductor layer grows with optimal crystal quality and orientation, improving light emission efficiency while maintaining cost-effectiveness
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 a high-quality, inexpensive A-plane group III nitride semiconductor layer on R-plane sapphire substrates, improving the efficiency and reducing production costs for long-wavelength LEDs by achieving a flat and crystalline surface, suitable for use in light-emitting devices.
Implementation Method 1
using metal organic chemical vapor deposition (MOCVD)
Implementation Method 2
epitaxial growth of group III nitride semiconductor crystals thereon
Data Source
AI summary
An object of the present invention is to provide a group III nitride semiconductor stacked structure having a high-quality A-plane group III nitride semiconductor layer on an R-plane sapphire substrate.The inventive group III nitride semiconductor stacked structure comprises a substrate composed of R-plane sapphire (α-Al2O3), a buffer layer composed of aluminum gallium nitride (AlxGa1-xN: 0≦X≦1) formed on said substrate and an underlying layer composed of an A-plane group III nitride semiconductor (AlxGayInzN1-aMa: 0≦X≦1, 0≦Y≦1, 0≦Z≦1, and X+Y+Z=1; wherein, M represents a group V element other than nitrogen (N), and 0≦a≦1) formed on said buffer layer, wherein the pit density of the surface of said underlying layer is 1×1010 cm−2 or less.