Multi-Electrode High-Voltage Transistor for GaN Cascode Ringing
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Solution Overview
Problem
Silicon-based transistors face significant power loss and reduced switching efficiency in high-voltage applications due to increased breakdown voltage and device capacitance, which is exacerbated by the ringing phenomenon when used in cascode configurations with high electron mobility transistors like GaN HEMTs.
Innovation Solution
The implementation of multi-electrode control structures in high-voltage transistors, including a substrate with a 2DEG layer, a control gate, and a field electrode, which are structurally and electrically isolated to prevent charge sharing and sustain capacitances, allowing for faster switching with reduced power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-voltage device (GaN HEMT) is used in a cascode configuration with a silicon-based transistor, then the breakdown voltage is improved and power density is increased, but excessive ringing occurs between the silicon-based transistor and the high-voltage device
Solution Approach 1:
A ringing suppressor is introduced as an intermediary component connected to the control gate of the high-voltage device. This suppressor acts as a mediator that absorbs and dampens the ringing oscillations between the silicon-based transistor and the GaN HEMT, eliminating the harmful oscillatory behavior while preserving the high-voltage operation capability of the cascode configuration.
2Object-generated harmful factors
If a ringing suppressor is placed at the control gate of the high-voltage device to suppress ringing, then the ringing phenomenon is reduced, but power loss increases and switching efficiency decreases
Solution Approach 1:
The invention changes the electrical parameters of the control gate by introducing a multi-electrode structure with separate control gates (first control gate and second control gate) that can be independently biased. By adjusting the voltage parameters applied to each control gate, the device achieves effective ringing suppression without the need for additional dissipative components, thereby maintaining low power loss and high switching efficiency.
3Strength
If the breakdown voltage of a silicon-based transistor is increased for high-voltage applications, then the transistor can operate at higher voltages, but channel resistance increases disproportionately and switching efficiency slows down
Solution Approach 1:
The invention segments the transistor structure into a cascode configuration with a silicon-based transistor and a high-voltage device (GaN HEMT), where each component operates in its optimal voltage range. The silicon-based transistor handles low-voltage switching operations with fast switching efficiency, while the GaN HEMT handles high-voltage blocking with high breakdown voltage capability. This segmentation allows the system to achieve both high breakdown voltage and fast switching efficiency by distributing functions across specialized components.
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 enables high-voltage operation with lower power loss and shorter switching times by isolating field electrodes from control and source/drain nodes, thereby minimizing parasitic capacitances and enhancing switching performance.
Implementation Method 1
a 2-dimension electron gas (2DEG) layer, a source node, a control gate, and a field electrode. The substrate can be a layer of silicon, above which the 2DEG layer is disposed. The 2DEG layer has a first end and a second end, both of which extend across a channel region of the HEMT structure.
Implementation Method 2
The control gate of the HEMT structure is disposed above the channel, and it is configured to mobilize charges along the channel in response to a gate-source voltage. The control gate establishes a gate-source capacitance (CGS) with the source node, as well as a gate-drain capacitance (CGD) with the drain node.
Implementation Method 3
The field electrode of the HEMT structure is disposed above the channel, and it is configured to spread the mobilized charges in response to a field voltage. The field electrode is structured and routed to prevent charge sharing with any one of the drain node, source node, or control gate.
Data Source
AI summary
A high-voltage transistor (HVT) structure adapts a low-voltage transistor (LUT) to high-voltage environments. The HVT structure includes a drain node, a source node, a control gate, and a field electrode. The drain node and the source node define a conductive channel, in which mobilized charges are regulated by the control gate. While being isolated from the control gate, the field electrode is configured to spread the mobilized charges in response to a field voltage. The field electrode is structured and routed to prevent charge sharing with any one of the drain node, source node, or control gate. Advantageously, the isolated field electrode minimizes the capacitance of the control gate as well as the drain and source nodes, such that the HVT can switch with less power loss and a more robust performance in a high-voltage environment.