GaN HEMT Buffer Structure for Short-Channel Leakage Control
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Solution Overview
Problem
Field-effect transistors used in high-frequency power amplifiers face challenges with short-channel effects, such as increased off-leakage current and threshold voltage rise due to electron injection into the substrate-side buffer layer, leading to signal quality deterioration in wireless communication systems when high drain voltages are applied.
Innovation Solution
A semiconductor device with a SiC substrate, an AlN nucleation layer, an AlGaN buffer layer with decreasing Al composition ratio, and a GaN channel layer, where the AlN nucleation layer thickness is less than or equal to 30 nm, suppressing electron injection and reducing time variation of the drain current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impurities such as iron or carbon are added to the buffer layer to suppress short-channel effects, then short-channel effects are suppressed, but signal quality deteriorates due to time variation of drain current
Solution Approach 1:
The patent extracts the harmful function of the deep energy level (electron trapping) from the buffer layer by removing impurities, while maintaining the beneficial short-channel effect suppression through a different mechanism (optimized AlN layer thickness and AlGaN composition gradient)
Solution Approach 2:
The patent changes the thickness parameter of the AlN nucleation layer to ≤30 nm and adjusts the Al composition ratio gradient in the AlGaN buffer layer, transforming the suppression mechanism from electron trapping to electric field modulation without deep energy levels
2Reliability
If a thick AlN nucleation layer is used to suppress short-channel effects, then short-channel effects are suppressed, but time variation of drain current increases
Solution Approach 1:
The patent optimizes the thickness parameter of the AlN nucleation layer to ≤30 nm, which is sufficiently thick to suppress short-channel effects but thin enough to minimize charge accumulation and reduce time variation of drain current
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 semiconductor device effectively suppresses time variation of the drain current, improving signal quality by reducing the potential barrier and minimizing charge accumulation at interfaces, thereby maintaining stable amplifier gain in high-frequency applications.
Implementation Method 1
the AlN nucleation layer becomes a potential barrier. Thus, there is a possibility that charges at an interface between the AlGaN buffer layer and the AlN nucleation layer and at an interface between the AlN nucleation layer and the substrate may be charged or discharged upon application of a high drain voltage
Implementation Method 2
the AlGaN buffer layer has an Al composition ratio decreasing from the SiC substrate toward the GaN channel layer
Data Source
AI summary
A semiconductor device according to the present disclosure includes a SiC substrate, an AlN nucleation layer provided on the SiC substrate, an AlGaN buffer layer provided on the AlN nucleation layer, a GaN channel layer provided on the AlGaN buffer layer, an AlGaN barrier layer provided on the GaN channel layer and a drain electrode, a source electrode, and a gate electrode each provided above the AlGaN barrier layer, wherein the AlGaN buffer layer has an Al composition ratio decreasing from the SiC substrate toward the GaN channel layer, and a thickness of the AlN nucleation layer is less than or equal to 30 nm.