N-type AlN Substrate for Vertical Nitride Devices
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Solution Overview
Problem
Conventional methods for producing n-type aluminum nitride single crystal substrates with high crystalline quality and thickness for vertical nitride semiconductor devices face challenges in achieving low dislocation density and suitable Si content, leading to inadequate withstand voltage characteristics.
Innovation Solution
The development of an n-type aluminum nitride single crystal substrate with a dislocation density of 10^6 cm^-2 or less and Si content between 3×10^17 to 1×10^20 cm^-3, along with the formation of electrode layers on both principal planes, enables the creation of high-performance vertical nitride semiconductor devices such as Schottky barrier diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the n-type aluminum nitride single crystal layer is formed on foreign substrate such as SiC substrate by MOVPE or HVPE, then the substrate can be produced, but the crystalline quality is insufficient and dislocation density is high
Solution Approach 1:
The patent applies homogeneity by using an aluminum nitride single crystal substrate as the base substrate, which has the same material composition and crystal structure as the layer to be grown. This material matching eliminates lattice mismatch and thermal expansion differences, resulting in significantly reduced dislocation density and improved crystalline quality of the n-type aluminum nitride single crystal layer.
Solution Approach 2:
The patent uses an aluminum nitride single crystal substrate as a template or copy of the desired crystal structure. By growing the n-type layer on this identical crystal structure, the high crystalline quality and low dislocation density are replicated and maintained in the grown layer, avoiding the defects that occur when growing on foreign substrates like SiC.
2Reliability
If the n-type aluminum nitride single crystal layer is grown on aluminum nitride freestanding substrate, then the dislocation density is reduced to 5×10^9 cm^-2, but the layer thickness is limited to 10 μm or less
Solution Approach 1:
The patent applies parameter changes by optimizing the Si doping concentration within the specific range of 3×10^17 to 1×10^20 atoms/cm³. This controlled doping enables the growth of thicker single crystal layers (50-500 μm) while maintaining low dislocation density and n-type conductivity, overcoming the thickness limitation of conventional undoped or lightly-doped layers.
Solution Approach 2:
The patent performs preliminary doping with Si during the crystal growth process itself, rather than attempting to dope pre-grown undoped layers. This in-situ doping during growth ensures uniform distribution of dopants throughout the thick layer, enabling the formation of electrically active n-type conductivity in the final thick substrate structure.
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 results in improved withstand voltage characteristics and enhanced performance of vertical nitride semiconductor devices, with reduced electron scattering and increased conductivity, effectively addressing the limitations of previous methods.
Implementation Method 1
n-type conductive single crystal aluminum nitride substrate (the n-type aluminum nitride single crystal substrate) doped with Si
Implementation Method 2
high dielectric breakdown voltage (12 MV/cm)
Data Source
AI summary
A vertical nitride semiconductor device includes an n-type aluminum nitride single-crystal substrate having an Si content of 3×1017 to 1×1020 cm−3 and a dislocation density of 106 cm−2 or less. An ohmic electrode layer is formed on an N-polarity side of the n-type aluminum nitride single-crystal substrate.