Jul 22 (Wed): "Design, Fabrication and Characterization of Highly Linear N-Polar GaN MIS-HEMTs for mm-Wave Receiver Applications," Pawana Shrestha, ECE PhD Defense

https://ucsb.zoom.us/j/98642054420?pwd=VkpuM0c4L01Ed0tobFlIeUNYd3Q5UT09

ABSTRACT

Gallium Nitride is widely employed for microwave and mm-wave applications. Though GaN HEMTs have primarily been used for power amplification, they are also well suited for receiver applications. In the receiver front-end, the linearity of an RF transistor is an important requisite. In a crowded wireless spectrum with large in band interferers, non-linearities can mask or distort a weak desired signal. At mm-wave frequencies and high data rates, circuit-level linearization techniques increase system complexity. Therefore, this study focuses on linearization at the device-level.

Traditionally, GaN is grown and fabricated in the Ga-polar orientation. In the N-polar orientation, the inverse polarization fields enable the implementation of device structures that provide excellent mm-wave performance. The devices presented in this work are based on N-polar GaN MIS-HEMT technology and are designed to achieve high gain and high linearity, simultaneously. I will present the device architecture, discuss the fabrication process and analyze the linearity characterization at 30 GHz. The linearity performance is described through OIP3 and OIP3/Pdc. An OIP3 of 32 dBm, OIP3/Pdc of 15 dB and 12.7 dB transducer gain at 30 GHz were obtained at a bias specific for high linearity. A strategy to achieve high linearity over a wide input bias range using derivative superposition at the device-level with a dual-threshold voltage device is discussed. The results of the first demonstration of a dual-threshold voltage N-polar GaN transistor are shown.

Hosted by: Professor Umesh Mishra

Submitted by: Pawana Shrestha <pawana@ece.ucsb.edu>