GaN HEMT Cap Layer Recess for Leakage Reduction
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Solution Overview
Problem
AlGaN/GaN high-electron mobility transistors (HEMTs) face issues with unstable threshold voltage and off-state leakage due to the GaN cap layer, which affects their reliability and performance in power electronic applications.
Innovation Solution
Selectively etching a portion of the GaN cap layer under the gate of the HEMT creates a discontinuity, reducing the off-state leakage current and stabilizing the threshold voltage by altering the electrical field distribution and reducing carrier trapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a GaN cap layer is used in AlGaN/GaN HEMTs, then the device structure is completed and manufacturing is enabled, but the threshold voltage becomes unstable and off-state leakage increases
Solution Approach 1:
The GaN cap layer is segmented by creating a recess that removes a portion of the cap layer, dividing it into regions with different thicknesses. This segmentation allows the device to maintain the benefits of the GaN cap layer while eliminating the harmful effects in specific areas, thereby stabilizing the threshold voltage and reducing off-state leakage.
Solution Approach 2:
The recess creates a localized modification in the GaN cap layer structure, where the cap layer thickness varies across different regions. This local quality change enables the device to have different electrical characteristics in different areas, specifically reducing carrier trapping and improving threshold voltage stability in the recessed region while maintaining overall device functionality.
2Ease of manufacture
If a GaN cap layer is used in AlGaN/GaN HEMTs, then the device structure is completed, but off-state leakage current increases
Solution Approach 1:
The GaN cap layer is segmented by creating a recess that removes a portion of the cap layer, dividing it into regions with different thicknesses. This segmentation allows the device to maintain the benefits of the GaN cap layer while eliminating the harmful effects in specific areas, thereby stabilizing the threshold voltage and reducing off-state leakage.
Solution Approach 2:
The recess structure converts the harmful effect of the GaN cap layer (which causes off-state leakage) into a beneficial effect by creating a region where the cap layer is thinner or absent, thereby reducing carrier trapping and lowering off-state leakage current while maintaining the overall device structure.
3Reliability
If the GaN cap layer is selectively etched to reduce off-state leakage, then threshold voltage stability improves, but the device structure becomes more complex
Solution Approach 1:
The GaN cap layer is segmented by creating a recess that removes a portion of the cap layer, dividing it into regions with different thicknesses. This segmentation allows the device to maintain the benefits of the GaN cap layer while eliminating the harmful effects in specific areas, thereby stabilizing the threshold voltage and reducing off-state leakage.
Data Source
AI summary
An electronic device, that in various embodiments includes a first semiconductor layer comprising a first group III nitride. A second semiconductor layer is located directly on the first semiconductor layer and comprises a second different group III nitride. A cap layer comprising the first group III nitride is located directly on the second semiconductor layer. A dielectric layer is located over the cap layer and directly contacts the second semiconductor layer through an opening in the cap layer.