Si-Doped AlN Buffer Layer for III Nitride Epitaxial Substrates
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Solution Overview
Problem
III nitride semiconductor epitaxial substrates face challenges in achieving high crystallinity and surface flatness due to lattice mismatch and thermal expansion differences with substrates, leading to dislocation issues and irregularities, which result in reduced quantum efficiency and potential device failure from cracks and double peaks in electroluminescence spectra.
Innovation Solution
A III nitride semiconductor epitaxial substrate is developed with a Si-doped AlN buffer layer having an Si concentration of 2.0×10^19/cm^3 and a thickness of 4 to 10 nm, combined with a superlattice laminate structure, which alternately stacks high and low Al-content layers to reduce dislocations and strain, thereby improving surface flatness and preventing crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a buffer layer made of AlN is doped with Si to reduce dislocations, then dislocation density is reduced, but abrupt irregularities appear on the surface of the buffer layer
Solution Approach 1:
The patent applies local quality by creating a Si-doped AlN buffer layer with specific localized properties (Si concentration of 1×10^19 to 1×10^20 atoms/cm³ and thickness of 3-15 nm) at the interface between the substrate and the III nitride semiconductor layer. This localized doping region reduces dislocations without causing widespread surface irregularities, as the doping is confined to a specific thickness range rather than being uniform throughout the entire buffer layer.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the Si concentration (1×10^19 to 1×10^20 atoms/cm³) and thickness (3-15 nm) of the Si-doped AlN buffer layer. By optimizing these parameters, the patent achieves a balance where sufficient Si doping reduces dislocation density while the controlled thickness prevents the formation of abrupt surface irregularities that would occur with higher doping levels or thicker layers.
2Manufacturing precision
If high concentration Si doping is applied to GaN buffer layer to reduce dislocations, then dislocation density is reduced, but growth mode changes from two-dimensional to three-dimensional island growth
Solution Approach 1:
The patent uses an AlN buffer layer as an intermediary material between the substrate and the III nitride semiconductor layer. This AlN buffer layer is doped with Si at controlled concentrations, serving as a mediator that reduces dislocations without triggering the three-dimensional island growth mode. The AlN composition acts as an intermediate step that allows Si doping to reduce dislocations while maintaining two-dimensional growth characteristics.
Solution Approach 2:
The patent changes the material composition parameter by using AlN instead of GaN for the buffer layer, and precisely controls the Si concentration (1×10^19 to 1×10^20 atoms/cm³) and thickness (3-15 nm). This parameter optimization allows the buffer layer to reduce dislocation density while maintaining a flat surface and two-dimensional growth mode, avoiding the harmful effects of high-concentration Si doping in GaN buffers.
3Manufacturing precision
If Si-doped AlN buffer layer with high Si concentration is used to improve surface flatness, then surface flatness is improved, but cracks are formed in the light emitting device
Solution Approach 1:
The patent optimizes the Si concentration parameter to a specific range (1×10^19 to 1×10^20 atoms/cm³) and controls the buffer layer thickness (3-15 nm). This precise parameter control achieves sufficient surface flatness for high-quality III nitride semiconductor growth while preventing the excessive Si concentration that would cause cracks and device failure. The optimized parameters balance surface quality with mechanical integrity.
Solution Approach 2:
The patent applies partial Si doping rather than excessive doping. By using a moderate Si concentration (1×10^19 to 1×10^20 atoms/cm³) and limited thickness (3-15 nm), the patent achieves the necessary surface flatness improvement without applying excessive Si that would lead to crack formation. This partial action approach provides just enough doping benefit without the harmful effects of over-doping.
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
The solution achieves excellent surface flatness, suppresses crack formation, and ensures a normal single-peak electroluminescence spectrum, enhancing the performance and reliability of III nitride semiconductor light emitting devices.
Implementation Method 1
an Si-doped AlN buffer layer having an Si concentration of 2.0×10^19/cm^3 or more and a thickness of 4 nm to 10 nm
Implementation Method 2
a superlattice laminate structure, which alternately stacks high and low Al-content layers to reduce dislocations and strain
Implementation Method 3
III nitride semiconductors are formed by performing epitaxial growth on a substrate
Data Source
AI summary
A III nitride semiconductor epitaxial substrate having more excellent surface flatness is provided, in which the problems of crack formation and the double peaks in the shape of the EL spectrum are mitigated by employing appropriate conditions for Si doping on an AlN layer on a substrate; a III nitride semiconductor light emitting device; and methods of producing the same. A III nitride semiconductor epitaxial substrate has a substrate of which at least a surface portion is made of AlN, an undoped AlN layer formed on the substrate, an Si-doped AlN buffer layer formed on the undoped AlN layer, and a superlattice laminate formed on the Si-doped AlN buffer layer. The Si-doped AlN buffer layer has an Si concentration of 2.0×1019/cm3 or more and a thickness of 4 nm to 10 nm.