Adjustable Field Effect Rectifier With Graded Doping Profile
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Solution Overview
Problem
Field Effect Rectifiers face limitations at high voltages due to negative resistance regions, which are undesirable in rectifiers, and struggle with rapid switching between forward and reverse current conduction, leading to electromagnetic interference issues.
Innovation Solution
The introduction of an Adjustable Field Effect Rectifier (AFER) with an adjustment pocket allows for modification of the top layer resistance through ion implantation, reducing negative resistance and improving reverse recovery characteristics, enabling operation at high voltages without electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Field Effect Rectifiers operate at high voltages, then power handling capability is improved, but negative resistance regions appear causing unstable operation
Solution Approach 1:
The patent applies local quality by creating a non-uniform doping profile in the drift region, specifically implementing a lightly-doped extension region adjacent to the depletion region. This localized modification of doping concentration (changing from uniform to graded profile) addresses the negative resistance issue at the specific location where it occurs (at the depletion region boundary) while maintaining high voltage blocking capability in other regions. The selective doping adjustment resolves the contradiction between high power handling and operational stability.
Solution Approach 2:
The patent changes the doping parameter profile in the drift region from uniform to graded by introducing a lightly-doped extension region with lower doping concentration than the main drift region. This parameter change (doping concentration gradient) eliminates the negative resistance region that causes unstable operation at high voltages, while preserving the high breakdown voltage characteristic. The controlled variation of doping concentration as a parameter resolves the technical contradiction.
2Speed
If Field Effect Rectifiers switch rapidly between forward and reverse current conduction, then response speed is improved, but electromagnetic interference increases
Solution Approach 1:
The patent implements beforehand cushioning by pre-configuring the drift region with a graded doping profile including a lightly-doped extension region. This structural preparation reduces the magnitude of current surges and voltage spikes that occur during rapid switching transitions. By anticipating the switching transients and having the graded profile in place beforehand, the device minimizes electromagnetic interference generation while maintaining fast switching capability, thus resolving the contradiction between speed and harmful emissions.
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 AFER device operates reliably and efficiently at high voltages without negative resistance, facilitating fast recovery and high-frequency operation while minimizing electromagnetic interference.
Implementation Method 1
The process for fabricating a device according to the invention comprises opening the gate oxide followed by ion implantation to create a dopant concentration below that opening.
Implementation Method 2
Other approaches, based on the field effect under an MOS gate, have been proposed in order to combine the high efficiency of a SBD with the high reliability of PN junction diodes.
Data Source
AI summary
An Adjustable Field Effect Rectifier uses aspects of MOSFET structure together with an adjustment pocket or region to result in a device that functions reliably and efficiently at high voltages without significant negative resistance, while also permitting fast recovery and operation at high frequency without large electromagnetic interference.