Vertical GaN Superjunction JFET/MOSFET Structure for Low On-Resistance
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Solution Overview
Problem
Conventional power electronics face challenges in achieving low specific on-resistance while maintaining high breakdown voltages, leading to increased die size and power loss in power conversion applications.
Innovation Solution
The use of vertical junction field-effect transistor (JFET) and metal-oxide field-effect transistor (MOSFET) devices with super junction structures, specifically employing III-nitride substrates and epitaxially regrown layers with varying dopant concentrations to reduce specific on-resistance up to 10-100 times without compromising breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional power electronic devices are used, then breakdown voltage can be maintained, but specific on-resistance increases and die size increases
Solution Approach 1:
The drift layer is segmented into multiple regions with different doping concentrations (first doping concentration in bulk, second doping concentration in alternating regions). This segmentation creates a superjunction structure that reduces the electric field peak, thereby reducing specific on-resistance while maintaining the required breakdown voltage through proper doping profile design.
Solution Approach 2:
Different regions of the drift layer are assigned different local doping concentrations to optimize performance. The alternating regions with higher doping concentration locally enhance charge density to reduce on-resistance, while the overall structure maintains sufficient depletion width for breakdown voltage. This local quality variation allows simultaneous optimization of both parameters.
2Strength
If drift layer thickness is increased to maintain breakdown voltage, then specific on-resistance increases
Solution Approach 1:
The doping concentration parameter is changed across different regions of the drift layer. By implementing alternating regions with different doping concentrations (second doping concentration higher than first), the electric field distribution is modified to reduce the peak field strength. This allows achieving the required breakdown voltage with a thinner effective drift layer, thereby reducing specific on-resistance and energy loss.
Solution Approach 2:
The drift layer is divided into alternating regions with different doping concentrations, creating a segmented structure that optimizes the electric field distribution. This segmentation enables the device to achieve high breakdown voltage through proper cumulative depletion width while reducing specific on-resistance through localized charge density enhancement in the alternating regions.
3Device complexity
If doping concentration is increased to reduce specific on-resistance, then breakdown voltage decreases
Solution Approach 1:
The drift layer is segmented into alternating regions with different doping concentrations. Regions with higher doping concentration (second doping concentration) are interspersed with regions of lower doping concentration (first doping concentration). This segmentation allows the high-doping regions to contribute to reducing specific on-resistance through increased charge density, while the low-doping regions maintain sufficient depletion width for achieving the required breakdown voltage.
Solution Approach 2:
Different local doping concentrations are assigned to different regions of the drift layer to simultaneously address on-resistance and breakdown voltage requirements. The alternating regions with higher doping concentration locally enhance charge density to reduce on-resistance, while the overall periodic structure ensures sufficient cumulative depletion width for breakdown voltage through proper design of region dimensions and doping profiles.
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 approach results in improved performance characteristics, including lower specific on-resistance, faster reverse recovery time, and reduced gate charge, enabling more efficient power conversion with smaller die sizes for given on-resistance targets.
Implementation Method 1
epitaxially regrowing a second III-nitride structure in the trenches, wherein the second III-nitride structure is characterized by a second conductivity type opposite to the first conductivity type
Data Source
AI summary
A method for manufacturing a vertical JFET includes providing a III-nitride substrate having a first conductivity type and forming a first III-nitride layer coupled to the III-nitride substrate. The first III-nitride layer is characterized by a first dopant concentration and the first conductivity type. The method also includes forming a plurality of trenches within the first III-nitride layer and epitaxially regrowing a second III-nitride structure in the trenches. The second III-nitride structure is characterized by a second conductivity type. The method further includes forming a plurality of III-nitride fins, each coupled to the first III-nitride layer, wherein the plurality of III-nitride fins are separated by one of a plurality of recess regions, and epitaxially regrowing a III-nitride gate layer in the recess regions. The III-nitride gate layer is coupled to the second III-nitride structure and the III-nitride gate layer is characterized by the second conductivity type.