Circular-Gate HEMT Structure for Low Off-State Leakage
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Solution Overview
Problem
Conventional High Electron Mobility Transistors (HEMTs) face challenges with device isolation, leading to issues such as shifted pinch-off voltage and high source-to-drain off-state leakage current, especially under high drain voltage, due to conventional isolation techniques and edge effects.
Innovation Solution
The design incorporates a three-dimensional structure with circular or partial-circle gates and sources, using dielectric layers for connections that avoid breaking the gate or source circles, providing natural device isolation and reducing edge effects, and optionally includes ion implantation for additional isolation without affecting the pGaN material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional isolation techniques are used, then device isolation is achieved, but source-to-drain off-state leakage current increases
Solution Approach 1:
The patent extracts or removes the conventional isolation techniques that were causing harmful edge effects and leakage current. By eliminating dielectric isolation layers and via connections near the source and drain regions, the device avoids creating electric field distortions that lead to increased source-to-drain leakage current in off-state operation.
Solution Approach 2:
The patent converts the potential harm of having no isolation structures into a benefit by utilizing the natural heterojunction boundaries to provide isolation. The heterojunction interface, which creates the 2DEG channel, also serves as a natural isolation boundary that prevents leakage current while maintaining device isolation, turning what could be a source of leakage into a protective feature.
2Ease of operation
If via connections through dielectric layers are used, then electrical connections are achieved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent removes dielectric isolation layers and via connections from the device structure. By eliminating these intermediate isolation structures, the device achieves electrical connections directly through the heterojunction interface, significantly reducing device complexity and manufacturing steps while maintaining adequate electrical isolation through the natural heterojunction boundaries.
3Reliability
If conventional isolation techniques are used, then device isolation is achieved, but edge effects increase
Solution Approach 1:
The patent extracts or removes conventional isolation techniques such as dielectric layers and via connections that create sharp geometric boundaries and edge effects. By eliminating these isolation structures, the device avoids concentrating electric fields at isolation interfaces, thereby reducing edge effects and their associated harmful impacts on device performance and reliability.
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 design enhances reliability by maintaining desired pinch-off characteristics, reduces on-resistance, and improves thermal dissipation, while avoiding the negative effects of conventional isolation methods, suitable for high power and high-frequency applications.
Implementation Method 1
a current channel formed using a heterojunction at a boundary between two materials having different band gaps. For example, a relatively wide band gap material such as AlGaN (Aluminum Gallium Nitride) may be doped with n-type impurities and used to form a junction with an undoped, relatively narrow band gap material, such as GaN (Gallium Nitride). Then, an equilibrium is reached in which the narrow band gap material has excess majority carriers that form a 2-dimensional electron gas (2DEG).
Implementation Method 2
the narrow band gap material has excess majority carriers that form a 2-dimensional electron gas (2DEG)
Implementation Method 3
a drain contact connected to the drain with a drain via connection through at least one dielectric layer. The HEMT device may include a source contact connected to the source with a source via connection through the at least one dielectric layer, and a gate contact connected to the circular gate with a gate via connection through the at least one dielectric layer.
Data Source
AI summary
High Electron Mobility Transistors (HEMTs) are described with a circular gate, with a drain region disposed within the circular gates and circular source region disposed around the circular gates. The circular gate and the circular source region may form complete circles.