Fabrication, characterization, and nonlinear modeling of GaN high electron mobility transistors

Date

2025-5

Author

Gürbüz, Abdulkadir

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Gallium nitride (GaN) has become a key material in defense, aerospace, and commercial applications due to its superior electrical and thermal properties. The success of GaN high electron mobility transistor (HEMT) based circuits heavily depends on the availability of accurate compact models that ensure first-pass design success. In this thesis, the widely accepted ASM-HEMT model was critically evaluated, and its limitations in S-parameter fitting were addressed through targeted model enhancements. A detailed analysis revealed that discrepancies in the model were linked to n-type doping within the channel region. This insight, supported by TCAD simulations, led to the development of an updated epitaxial design featuring a lower conductivity channel. Fabricated devices based on the new structure demonstrated strong agreement between experimental results and model predictions. The modifications introduced in the model enhance the reliability and scalability of GaN HEMT modeling across a wider range of bias conditions, contributing to more accurate and efficient circuit design for next-generation GaN technologies. In addition, a novel surface treatment method proposed for application prior to gate metal deposition has led to a 25-fold reduction in gate leakage current levels, while significantly improving the wafer-level gate leakage current uniformity. The applied treatment preserves the overall RF and DC performance of the device and improves the trap energy levels associated with gate leakage mechanisms, according to gate leakage modeling results.

Subject Keywords

GaN HEMT, Nonlinear modeling, ASM-HEMT, TCAD, GaN epitaxy

URI

https://hdl.handle.net/11511/115091

Collections

Graduate School of Natural and Applied Sciences, Thesis