Stitched Gate GaN HEMT Breakdown Voltage
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Solution Overview
Problem
Gallium Nitride High Electron Mobility Field Effect Transistors (HEMTs) face the challenge of preventing short circuiting between the gate and drain due to breakdown of the barrier layer under high electric fields, leading to increased dynamic on resistance and reduced breakdown voltage.
Innovation Solution
The implementation of a HEMT device with a plurality of physically distinct subgates electrically connected through a field plate, arranged in staggered rows with each subgate being approximately 0.05 micrometers in radius, to reduce dynamic on resistance and increase breakdown voltage between the gate and drain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single monolithic gate is used in GaN HEMT, then the device structure is simple, but the breakdown voltage between gate and drain decreases due to high electric field concentration
Solution Approach 1:
The gate is divided into multiple physically distinct subgates (first subgate, second subgate, third subgate, etc.) arranged in a stitched configuration. Each subgate is separated by isolation regions, which distributes the electric field and prevents concentration at single points, thereby increasing the breakdown voltage between gate and drain while maintaining a manageable structural complexity through systematic arrangement.
Solution Approach 2:
Isolation regions are introduced as intermediary elements between adjacent subgates. These isolation regions act as mediators that electrically isolate individual subgates from each other, preventing direct electrical breakdown paths between them while allowing the subgates to collectively form the gate structure. This intermediary structure enables higher breakdown voltage by blocking breakdown propagation between subgates.
2Strength
If the barrier layer thickness is increased to prevent breakdown, then the breakdown voltage increases, but the dynamic on resistance increases
Solution Approach 1:
The gate is segmented into multiple subgates with isolation regions between them. This segmentation allows the barrier layer to be optimized for breakdown voltage without requiring excessive thickness, because the isolation regions prevent breakdown propagation. The subgates can be closely spaced while maintaining electrical isolation, enabling thin barrier layers that support high electron density and low on-resistance while still achieving high breakdown voltage through the stitched configuration.
Solution Approach 2:
The invention changes the electrical parameters of the gate structure by introducing isolation regions that modify the electric field distribution. This allows the barrier layer thickness to be optimized independently - thin enough to maintain low on-resistance through high electron density, yet sufficient to provide the required breakdown voltage when combined with the stitched gate configuration that distributes and controls the electric field.
Data Source
AI summary
Principles of the present invention reduces the maximum electric field strength between a gate and a source or drain in a FET by breaking up the usually monolithic gate into a plurality of physically separate subgates that are electrically connected into one or more groups.