AlGaN Semiconductor Device with Reverse-Tapered Electrode Structure
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Solution Overview
Problem
Current semiconductor devices using nitride semiconductors face challenges in achieving improved characteristics, particularly in controlling current flow and obtaining high threshold voltages, which are essential for reliable operation.
Innovation Solution
The semiconductor device incorporates a specific structure with AlxGa1-xN regions and insulating members, where the third electrode is positioned between the first and second electrodes, and the semiconductor regions are configured with partial regions and insulating portions to create a reverse-tapered configuration, aligning with the Z-axis direction, and utilizing a gate insulating film to control current flow and enhance threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitride semiconductor device is designed to achieve high threshold voltage, then the normally-off characteristic is improved, but the current flow control becomes difficult
Solution Approach 1:
The patent applies local quality by creating distinct AlGaN regions with different Al compositions (x1, x2, x3) at different locations within the semiconductor structure. The first AlGaN region has a first composition ratio, the second AlGaN region has a second composition ratio, and the third AlGaN region has a third composition ratio, where these ratios differ to create localized electrical properties that enable both high threshold voltage and controllable current flow in specific areas of the device.
Solution Approach 2:
The patent utilizes parameter changes by varying the Al composition ratio (x) in AlxGa1-xN across different regions and potentially across the thickness of the layers. By changing the composition parameter x from x1 to x2 to x3 in different AlGaN regions, the patent modifies the band structure and electrical characteristics to achieve the desired threshold voltage and current control properties simultaneously.
2Reliability
If the Al composition ratio is increased to improve threshold voltage, then the normally-off characteristic is enhanced, but the device complexity increases
Solution Approach 1:
The patent segments the semiconductor device into multiple functional regions: a first AlGaN region, a second AlGaN region, and a third AlGaN region, each with specific composition ratios. This segmentation allows the complex functionality of high threshold voltage and current control to be distributed across separate regions rather than requiring a single complex structure, making the overall device more manageable and manufacturable.
Solution Approach 2:
The patent employs composite materials by combining multiple AlGaN layers with different Al composition ratios (x1, x2, x3) to create a multi-layer heterostructure. This composite approach leverages the beneficial properties of each composition ratio - higher Al content regions provide higher threshold voltage while lower Al content regions facilitate current flow - achieving high performance without excessive overall complexity.
Data Source
AI summary
According to one embodiment, a semiconductor device includes first, second, and third electrodes, and first, second, and third semiconductor regions. The third electrode is between the first electrode and the second electrodes. The first semiconductor region includes Alx1Ga1-x1N and includes first to seventh partial regions. The fourth partial region is between the first partial region and the third partial region. The fifth partial region is between the third partial region and the second partial region. The second semiconductor region includes Alx2Ga1-x2N and includes first and second semiconductor portions. The sixth partial region is between the fourth partial region and the first semiconductor portion. The seventh partial region is between the fifth partial region and the second semiconductor portion. The third semiconductor region includes Alx3Ga1-x3N and includes a first semiconductor film part. The first semiconductor film part is between the sixth partial region and the third electrode.