Silicon-Doped AlN Substrate Conductivity
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Solution Overview
Problem
Current methods for forming high-quality n-type aluminum nitride single crystal substrates face challenges in achieving high n-type conductivity due to compensation by other impurities and point defects, which affects crystallinity and dislocation density, limiting their use in advanced semiconductor devices.
Innovation Solution
The development of a silicon-doped n-type aluminum nitride single crystal substrate with optimized growth conditions, including a specific ratio of luminescence spectrum intensities, electron concentration, and dislocation density, to enhance n-type conductivity and reduce the impact of compensating impurities and defects, resulting in a free-standing substrate suitable for vertical semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If n-type aluminum nitride single crystal layer is formed on foreign substrate (sapphire or SiC) by Si doping, then conductivity is improved, but crystalline quality and thickness sufficient for substrate use cannot be achieved
Solution Approach 1:
The patent uses an aluminum nitride single crystal base substrate as the foundation for growing the n-type aluminum nitride single crystal layer. This homogeneous material matching ensures lattice compatibility and minimizes dislocation density, enabling the formation of high-quality thick films suitable for substrate application while maintaining n-type conductivity through Si doping.
2Reliability
If n-type aluminum nitride single crystal layer is formed on foreign substrate, then conductivity is improved, but sufficient thickness for substrate use cannot be achieved
Solution Approach 1:
By using an aluminum nitride single crystal base substrate that matches the lattice structure of the grown layer, the patent eliminates lattice mismatch issues that would otherwise limit film thickness. This homogeneous material system allows continuous growth of thick n-type aluminum nitride layers with maintained crystalline quality and conductivity.
3Productivity
If sublimation method is used to grow thick group III nitride single crystal with Si impurity, then growth rate and crystallinity are improved, but other impurities and point defects compensate the n-type conductivity
Solution Approach 1:
The patent extracts and eliminates harmful impurities and point defects from the crystal structure through optimized growth conditions on aluminum nitride base substrates. This selective removal of compensating defects ensures that Si dopants effectively contribute to n-type conductivity while maintaining the benefits of high growth rate and good crystallinity from the sublimation method.
Solution Approach 2:
The patent optimizes growth parameters including temperature, pressure, and Si doping concentration during the sublimation process. By carefully controlling these parameters, the patent maximizes Si incorporation for n-type conductivity while minimizing the formation of compensating impurities and defects, achieving both high growth rate and reliable conductivity.
4Reliability
If Si doping is performed to increase n-type conductivity, then conductivity is improved, but other impurities and point defects compensate the conductivity and damage crystallinity
Solution Approach 1:
The aluminum nitride single crystal base substrate acts as an intermediary that facilitates controlled Si incorporation while preventing the formation of compensating defects. The matched lattice structure of the base substrate provides a template for high-quality crystal growth, allowing Si doping to enhance conductivity without sacrificing crystallinity.
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 approach enables the production of n-type aluminum nitride substrates with high n-type conductivity and low dislocation density, improving the reliability and performance of semiconductor devices such as Schottky barrier diodes and transistors by ensuring that a significant portion of doped silicon contributes to electron conduction.
Implementation Method 1
silicon is doped in an aluminum nitride single crystal
Implementation Method 2
a ratio (I1/I2) between a luminescence spectrum intensity (I1) of a peak at 370 to 390 nm and a luminescence peak intensity (I2) of a band edge of aluminum nitride
Data Source
AI summary
A silicon-doped n-type aluminum nitride monocrystalline substrate wherein, at a photoluminescence measurement at 23° C., a ratio (I1/I2) between the emission spectrum intensity (I1) having a peak within 370 to 390 nm and the emission peak intensity (I2) of the band edge of aluminum nitride is 0.5 or less; a thickness is from 25 to 500 μm; and a ratio (electron concentration/silicon concentration) between the electron concentration and the silicon concentration at 23° C. is from 0.0005 to 0.001.