Aug 28 (Mon) @ 3:30pm:” Millimeter-Wave GaN Device Modeling and Circuit Design,” Rohit Reddy Karnaty, ECE PhD Defense

Date and Time
Engineering Science Building (ESB), Room 2001

Zoom Meeting – Meeting ID: 842 8889 3104 | Passcode: 391931


Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs) offer significant advantages in microwave power applications, yet their scaling for high power in millimeter-wave (mmW) bands presents complex trade-offs involving device passivation, current collapse, and parasitic capacitance.

This research introduces a modified MIT Virtual Source GaN-HEMT (MVSG) model specifically for N-polar HEMTs, demonstrating its predictive accuracy. The rationale for adopting physics-based modeling and the necessity for adjustments in N-polar devices are detailed. Furthermore, a novel methodology is developed to extend the traditional single-threshold model to a dual-threshold device structure, enhancing its applicability.

With the emergence of 5G in mmW bands, power amplifiers (PAs) in various applications, from handsets to basestations, face rigorous performance demands. This work proposes a passive outphasing load modulation (POLM) approach as a versatile tuning method for different device technologies. The principles of POLM for achieving high average efficiency and its application to GaN PAs at 28 GHz are elaborated and validated through measurements.


Rohit Reddy Karnaty is a 5th-year PhD student in Professor Jim Buckwalter's RF & Mixed-signal Integrated Systems Laboratory group at the University of California, Santa Barbara. His research focuses on mm-Wave device modeling and circuit design of GaN devices. Rohit received his B.S. degree in Electrical Engineering from the Indian Institute of Technology, Madras, in 2016, and his M.S. in Electrical and Computer Engineering from the University of California, Santa Barbara, in 2018

Hosted by: Professor James F. Buckwalter

Submitted by: Rohit Reddy Karnaty <>