Cascode Rectifier Structure for Power Conversion Efficiency
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Solution Overview
Problem
Silicon-based power semiconductor devices face limitations in efficiency due to high voltage drops in forward conduction and longer reverse recovery times, leading to power losses and complex assembly issues with parasitics in power conversion systems.
Innovation Solution
A cascode rectifier structure integrating a group III-V semiconductor device with a silicon-containing rectifier device, providing a vertical conduction path and controlled breakdown voltage, which reduces power losses and improves forward conduction and reverse recovery times, while also addressing parasitic issues through a trench configuration that reduces stress and enhances thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick regions of lightly doped or intrinsically doped material are used to support high breakdown voltages, then breakdown voltage is improved, but forward conduction voltage drop increases
Solution Approach 1:
The patent employs a composite structure combining silicon-based devices with group III-V semiconductor devices (such as GaN or SiC). The silicon portion provides high breakdown voltage capability through its inherent material properties, while the group III-V portion contributes low forward conduction voltage drop due to its superior electron mobility and lower on-resistance. This heterogeneous integration allows the device to simultaneously achieve high voltage blocking capability and low conduction losses, resolving the fundamental trade-off in single-material power devices.
Solution Approach 2:
The power semiconductor device is divided into distinct functional regions: a silicon-based portion optimized for high voltage blocking with lightly doped drift regions, and a group III-V semiconductor portion optimized for low resistance conduction. Each material segment is strategically placed to perform its optimal function, with the silicon handling voltage stress and the group III-V handling current conduction, thereby eliminating the need for thick lightly doped regions that would increase forward voltage drop.
2Reliability
If higher voltage silicon-based devices are designed, then breakdown voltage is improved, but reverse recovery time increases
Solution Approach 1:
The hybrid silicon-group III-V structure enables high breakdown voltage through the silicon portion while achieving fast reverse recovery through the group III-V portion. The group III-V semiconductor material exhibits superior carrier sweep-out characteristics and lower stored charge due to its direct bandgap and higher saturation velocity, resulting in significantly reduced reverse recovery time compared to conventional silicon devices of the same voltage rating.
3Adaptability or versatility
If discrete power semiconductor devices are co-packaged with other electronic devices, then integration is achieved, but parasitics increase and assembly complexity increases
Solution Approach 1:
The patent integrates the silicon-based high voltage device and group III-V low voltage device into a single monolithic or closely coupled hybrid structure. This merging eliminates the need for separate discrete device packaging and interconnection, thereby reducing parasitic inductances and resistances associated with external bonds and traces. The integrated hybrid device can be directly mounted in power modules, simplifying assembly processes and reducing the number of packaging steps required.
Data Source
AI summary
A method for forming a cascode rectifier structure includes providing a group III-V semiconductor structure includes a heterostructure disposed on a semiconductor substrate. A first current carrying electrode and a second current carrying electrode are provided adjacent a major surface of the heterostructure and a control electrode is provided between the first and second current carrying electrode. A rectifier device is provided integrated with the group III-V semiconductor structure and is electrically connected to the first current carrying electrode and to a third electrode. The control electrode is provided further electrically connected to the semiconductor substrate and the second current path is generally perpendicular to a primary current path between the first and second current carrying electrodes. The cascode rectifier structure is provided as a two terminal device.