Nitride Semiconductor Substrate Interface Texture for Leakage Reduction
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Solution Overview
Problem
High electron mobility transistors require improvements in withstand voltage, reduction of leakage current, and current collapse, with existing technologies focusing on complex structures and not effectively addressing these needs.
Innovation Solution
A nitride semiconductor substrate with a first layer formed on a single crystal substrate, where the interface between the first layer and the nitride semiconductor layer has a specific surface texture and AlN layer characteristics, including a mean height difference and interval between convex and concave features, and adjusted Si concentration to reduce dislocations and improve substrate quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nitride semiconductor substrate structures are used, then the basic transistor function is achieved, but the withstand voltage is insufficient and leakage current is high
Solution Approach 1:
The invention applies local quality by creating a specific surface texture only at the interface between the first layer and nitride semiconductor layer, while maintaining other parts of the structure conventional. The convex top portions and concave bottom portions are localized features that modify dislocation behavior specifically at this interface, improving withstand voltage and reducing leakage current without changing the overall device structure
Solution Approach 2:
The first layer serves as an intermediary between the single crystal substrate and the nitride semiconductor layer. By controlling the surface texture of this intermediate layer, the invention mediates dislocation propagation, preventing harmful dislocations from reaching the active device regions while maintaining structural integrity
2Reliability
If complex structures are used to improve transistor characteristics, then performance parameters improve, but the device complexity increases
Solution Approach 1:
Instead of complexing the overall device structure, the invention applies a localized surface texture modification only at the critical interface region. This local modification effectively suppresses current collapse by controlling dislocation behavior without adding complex layers or structures throughout the entire device
Solution Approach 2:
The invention changes the surface texture parameters of the first layer (convex top portion height, concave bottom portion depth, and interval between them) to optimize current collapse performance. By adjusting these geometric parameters within specific ranges, effective current collapse suppression is achieved without increasing device complexity
Data Source
AI summary
A solution is formation of a nitride semiconductor layer on one principal plane of a single crystal substrate through a first layer. Upon selecting arbitrary three places in a radial direction from a cross section cleaved in a diameter portion and observing an interface between the first layer and the nitride semiconductor layer by taking a width of at least 500 nm in the radial direction, a value is within the range of 6 nm or more and 15 nm or less in a mean value of the three places with regard to a difference between a maximum height of a convex top portion and a minimum height of a concave bottom portion of the first layer in a thickness direction from the single crystal substrate toward the nitride semiconductor layer. A value is 10 nm or more and 25 nm or less in the mean value.