GaN HEMT Electrode Structure for High Current and Low On Resistance
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Solution Overview
Problem
Field-effect transistors face challenges in achieving high maximum current and low on resistance due to limitations in electrode structures, particularly with GaN-based HEMTs, where longer drain-gate distances are required for high breakdown voltage but result in larger source electrodes and reduced unit element density, limiting channel width and increasing contact resistance.
Innovation Solution
The electrode structure is optimized by having a source-gate distance shorter than the drain-gate distance, with source electrodes formed in smaller regions surrounded by gate electrodes, allowing for increased unit element density and longer total gate length, while maintaining adequate drain electrode size, thus enhancing maximum current and reducing on resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drain-gate distance is increased to achieve high breakdown voltage, then the breakdown voltage is improved, but the source electrode area increases excessively and unit element density decreases
Solution Approach 1:
The source electrode formation region is segmented and constrained to be smaller than the drain electrode formation region. By dividing the electrode structure into distinct formation regions with different size constraints, the source electrode area is prevented from increasing excessively while maintaining adequate drain-gate distance for breakdown voltage.
Solution Approach 2:
Different regions of the electrode structure are given different quality characteristics. The source electrode formation region is made smaller than the drain electrode formation region, creating local quality differences that optimize both breakdown voltage and unit element density without requiring excessive source electrode area.
2Reliability
If the source electrode area is increased to reduce contact resistance, then the contact resistance is improved, but the unit element density decreases and channel width is reduced
Solution Approach 1:
The electrode structure is segmented into distinct formation regions where the source electrode formation region is smaller than the drain electrode formation region. This segmentation allows optimization of contact resistance within the source region while preserving overall unit element density through the smaller footprint.
Solution Approach 2:
The size parameter of the source electrode formation region is changed to be smaller than that of the drain electrode formation region. This parameter change enables reduction of source electrode area while maintaining adequate contact properties, thereby increasing unit element density and channel width.
3Productivity
If the unit element density is increased to achieve high maximum current, then the maximum current is improved, but the drain-gate distance must be reduced which lowers breakdown voltage
Solution Approach 1:
The electrode structure is divided into separate formation regions with optimized dimensions. The source electrode formation region is smaller than the drain electrode formation region, allowing increased unit element density for high maximum current while the drain region maintains adequate size for breakdown voltage requirements.
4Reliability
If the channel width is increased to reduce on resistance, then the on resistance is improved, but the electrode structure complexity increases
Solution Approach 1:
The electrode structure uses segmented formation regions with clear size relationships (source region smaller than drain region). This segmentation enables increased channel width for low on resistance while maintaining relatively simple fabrication through well-defined regional boundaries rather than complex interlaced patterns.
Data Source
AI summary
A field-effect transistor includes a plurality of unit elements which include a semiconductor layer having a first surface, a plurality of gate electrodes, drain electrodes, and source electrodes. Each of the plurality of gate electrodes is provided to define a drain electrode formation region which is surrounded by each of the plurality of gate electrodes. Each of the source electrodes is disposed in a source electrode formation region surrounded by the plurality of gate electrodes of the plurality of unit elements which are adjacent to each other. A source-gate distance between the each of the source electrodes and the each of the plurality of gate electrodes of the plurality of unit elements is shorter than a drain-gate distance between each of the drain electrodes and the each of the plurality of gate electrodes. The source electrode formation region is smaller than the drain electrode formation region.