Nitride Semiconductor Device with Alternating AlN-GaN Foundation Layers
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Solution Overview
Problem
Nitride semiconductor devices formed on silicon substrates face challenges such as defect generation and cracking due to lattice constant and thermal expansion coefficient differences, particularly when attempting to form thick n-type GaN layers.
Innovation Solution
A method involving the alternated stacking of AlN and GaN foundation layers on an AlN buffer layer, with a δ-doped layer in the substrate-side GaN foundation layer closest to the silicon substrate, and forming low- and high-concentration parts in the functional layer to reduce dislocation and crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a thick n-type GaN layer is formed on a silicon substrate, then the mass productivity is improved, but cracks are generated due to lattice constant and thermal expansion coefficient differences
Solution Approach 1:
The patent divides the foundation layer into multiple segments: an AlN buffer layer, multiple alternating AlN and GaN foundation layers (forming a superlattice structure), and functional layers. This segmentation allows each layer to serve specific functions in managing lattice mismatch and thermal stress, enabling thick GaN layer formation without cracks while maintaining high productivity on silicon substrates
Solution Approach 2:
The patent applies local quality by creating regions with different impurity concentrations within the GaN foundation layers (low-concentration and high-concentration parts). This local variation in composition allows optimization of specific properties in different regions to manage stress distribution and prevent crack formation while maintaining overall device performance
2Productivity
If nitride semiconductor devices are formed on silicon substrates, then mass productivity is improved, but defect density increases due to lattice constant difference
Solution Approach 1:
The segmented foundation layer structure with alternating AlN and GaN layers acts as a dislocation filter, where each interface blocks and redistributes misfit dislocations. This segmentation approach maintains high crystal quality in the functional layers while enabling production on cost-effective silicon substrates
Solution Approach 2:
The AlN buffer layer and alternating AlN/GaN foundation layers serve as intermediary structures between the silicon substrate and the functional nitride semiconductor layers. These intermediary layers gradually transition the lattice mismatch, reducing defect propagation to the functional layers while maintaining compatibility with silicon substrates for high-volume production
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 a high-quality nitride semiconductor device with reduced defect density and crack suppression, enhancing the crystallinity and performance of the semiconductor layer.
Implementation Method 1
a defect and a crack are easily generated due to a difference in lattice constant or thermal expansion coefficient
Implementation Method 2
a defect and a crack are easily generated due to a difference in lattice constant or thermal expansion coefficient
Implementation Method 3
a method involving the alternated stacking of AlN and GaN foundation layers on an AlN buffer layer, with a δ-doped layer in the substrate-side GaN foundation layer closest to the silicon substrate, and forming low- and high-concentration parts in the functional layer to reduce dislocation and crack formation
Data Source
AI summary
According to one embodiment, a nitride semiconductor device (110, 111, 120) includes: a stacked foundation layer (50), and a functional layer (10s). The stacked foundation layer (50) is formed on an AIN buffer layer (55) formed on a silicon substrate (40). The stacked foundation layer (50) includes AIN foundation layers (52) and GaN foundation layers (51) being alternately stacked. The functional layer (10s) includes a low-concentration part (10l), and a high-concentration part (10h) provided on the low-concentration part (10l). A substrate-side GaN foundation layer (51 s) closest to the silicon substrate (40) among the plurality of GaN foundation layers (51) includes first portion (51a) and second portion (51b), and a third portion (51c) provided between the first and second portions (51a, 51b). The third portion (51c) has a Si concentration not less than 5 X 1018 cm-3 and has a thickness smaller than a sum of those of the first and second portions (51a, 51b).