| PhD Seminar

Name of the Speaker: Ms. Aishwarya Kaity (EE20D013)
Guide: Dr. Nandita Das Gupta
Co-Guide: Dr. Sayak Dutta Gupta
Venue: ESB-244 (Seminar Hall)
Date/Time: 10th November 2025 (Monday), 3:00 pm
Title: Novel AlGaN/GaN HEMT and MISHEMT with Non-Overlapping Source Field Plate (NOSFP) with improved figures of merit

Abstract :

GaN-based devices are well suited for high-voltage, high-current, and high-frequency applications due to their wide bandgap, high breakdown strength, and good thermal properties. The strong polarization at the AlGaN/GaN interface induces a two-dimensional electron gas (2DEG), forming a conductive channel with high carrier mobility, which supports fast switching and efficient power operation.

Although GaN offers higher breakdown fields than silicon, the breakdown voltage can be further improved through proper field-plate engineering, which redistributes the electric field along the channel. However, while field plates improve the breakdown voltage, the capacitances (Cgd and Cgs) are degraded. In this work, a novel Non-Overlapping Source Field Plate (NOSFP) structure has been proposed, which improves the breakdown voltage but does not degrade the capacitances. This work examines the effect of different field-plate designs on the electrical performance of AlGaN/GaN High Electron Mobility Transistors (HEMTs) and Metal–Insulator–Semiconductor HEMTs (MIS-HEMTs) through experimental investigation, validated by TCAD simulation. This study shows that the variations in field-plate geometry influence the electric field profile, breakdown voltage, and parasitic capacitances in fabricated AlGaN/GaN HEMT and MIS-HEMT devices. It also demonstrated experimentally that combining optimized field-plate structures with suitable gate dielectrics can shift the threshold voltage positively and reduce leakage currents.

Among the various designs investigated, the proposed HEMT and MIS-HEMT with Non-Overlapping Source Field Plate (NOSFP) structure exhibit superior figures of merit in both power and RF domains, as suggested by simulation and validated by actual measurement. A detailed dimensional and performance-based analysis of the devices with NOSFP structure further emphasises its potential for next-generation high-power GaN device applications.