GaN Transistor-Schottky Layout for Low Reverse Loss and Leakage
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Solution Overview
Problem
Current Group III nitride-based semiconductor devices with integrated Schottky barrier diodes face challenges in achieving superior reverse conduction capability without increasing forward conduction resistance, and existing solutions often result in high OFF-state leakage currents due to high electric fields around the Schottky contact edge.
Innovation Solution
An interdigitated GaN-based Schottky barrier diode/transistor structure is proposed, where the Schottky contact is integrated within the access region to enhance reverse conduction capability while maintaining low forward conduction resistance, utilizing a self-aligned gate process and source-connected field plates to optimize the design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Schottky barrier diode is integrated into a Group III nitride transistor device, then reverse conduction capability is improved, but OFF-state leakage current increases due to high electric fields around the Schottky contact edge
Solution Approach 1:
The source contact is segmented into multiple discrete source contact sections spaced apart from each other. The Schottky contact is positioned between adjacent source contact sections, creating distinct transistor sections and diode sections. This segmentation reduces the electric field concentration at the Schottky contact edge while maintaining reverse conduction capability, thereby reducing OFF-state leakage current.
Solution Approach 2:
Different regions of the device are assigned different functions: regions with gate electrode structures overlying them form transistor sections with controlled channel conductivity, while regions with Schottky contacts between source contact sections form diode sections for reverse conduction. This local differentiation allows optimal performance in each region while managing the trade-off between reverse conduction and leakage current.
2Area of stationary object
If Schottky contact is integrated within the access region, then area effectiveness is improved, but fabrication complexity increases
Solution Approach 1:
The Schottky contact and the source contact structure are merged into a single integrated contact region. The Schottky contact is formed between discrete source contact sections, combining the functions of source contact and Schottky diode contact in the same physical region. This merging improves area effectiveness by eliminating the need for separate diode and transistor contact regions.
Solution Approach 2:
The contact structure serves multiple functions: the discrete source contact sections provide ohmic contact for forward conduction, while the Schottky contact formed between them enables reverse conduction. This multi-functional design achieves both transistor and diode functionality within a single integrated structure, improving area effectiveness without requiring completely separate device regions.
3Loss of energy
If discrete source contact sections are used with Schottky contact between them, then reverse conduction loss is reduced, but forward conduction resistance may increase
Solution Approach 1:
The source contact is divided into multiple discrete sections with the Schottky contact positioned between them. This segmentation creates low-loss paths for reverse conduction through the Schottky contact while maintaining adequate ohmic contact area in each source contact section for forward conduction, balancing reverse conduction loss and forward conduction resistance.
Solution Approach 2:
The electrical parameters of the contact structure are optimized: the Schottky contact provides low forward voltage drop and low reverse conduction loss, while the discrete source contact sections maintain sufficient ohmic contact area to keep forward conduction resistance low. The spacing and dimensions of the discrete sections are tuned to achieve the optimal balance between reverse conduction efficiency and forward conduction resistance.
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 configuration achieves low reverse conduction voltage even with negative gate voltage, reducing reverse conduction loss and improving area effectiveness compared to two-device solutions, with a good trade-off between forward and reverse conduction performance.
Implementation Method 1
At least one Schottky metal contact is arranged between and spaced apart from neighbouring ones of the source contacts so that alternate Group III nitride transistor sections and Schottky barrier diode sections are formed
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
In an embodiment, a semiconductor device is provided that comprises a Group III nitride transistor device (22) and a Schottky barrier diode (23) integrated in a Group III nitride body (13). The semiconductor device comprises a common drain/cathode finger (15) arranged on the Group III nitride body, two or more source contacts (16) that are arranged on the Group III nitride body and spaced apart in a row, the row being spaced laterally apart from, and extending substantially parallel to, the common drain/cathode finger, a gate electrode structure (18) arranged on the Group III nitride body and one or more Schottky metal contacts (19) arranged on the Group III nitride body. At least one Schottky metal contact is arranged between and spaced apart from neighbouring ones of the source contacts. The gate electrode structure comprises a closed ring section (20) for each source contact that laterally surrounds that source contact, wherein neighbouring closed ring sections are connected by a gate connection section (21).