Oct 6 (Fri) @ 2:00pm: ”N-Polar GaN HEMTs with high power and efficiency at W and D-band,” Emre Akso, ECE PhD Defense

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


The growing demand for faster data transmission in wireless communications and high-resolution imaging for radar applications require high frequency transmitters with high power and efficiency. This thesis focuses on transistor-level improvements to push the power, gain, efficiency and operation frequency simultaneously. We demonstrate the first N-Polar GaN HEMTs with multi-fingers exhibiting record performance: 712 mW with 31.7% PAE and 1 W with 21.4% PAE. Both 712 mW and 1 W are the world-record power levels measured from a single transistor at W-band. With advanced scaling, we demonstrate world record linear gain and PAE with N-Polar GaN on Sapphire: At 10 V drain bias, the devices demonstrated peak PAE of 50.2 % (record) and linear gain of 10.5 dB (record) with peak POUT of 3.2 W/mm at 94 GHz. Finally, we demonstrate the first D-band (110-170 GHz) operation of N-Polar GaN HEMTs with CPW matching networks. Designed and fabricated pre-matched devices demonstrate D-band record power density of 2 W/mm with 10.6% PAE at 132 GHz (without de-embedding losses). In summary, this thesis demonstrates world-record performance for (1) total power from a single transistor at W-band, (2) gain and efficiency at W-band, and (3) power density at D-band, paving the way for the next generation ultra-fast communication systems and high-resolution imaging.


Emre Akso is currently a PhD candidate at the department of electrical and computer engineering (ECE) at UCSB. He received his MS degree in electrical engineering from UCSB  in 2020, and his BSc degree in electronics and communication engineering from Istanbul Technical University in 2018. His research interests include RF semiconductor device design, nanofabrication, modeling/characterization, as well as the RF circuit applications of such devices for high power, efficiency, linearity and low noise.

Hosted by: Professor Umesh Mishra

Submitted by: Emre Akso <emreakso@ucsb.edu>