Can Asymmetry Quench Self-Heating in MOS High Electron Mobility Transistors?

Author

MD SHAHRUL ISLAM, Southern Illinois University CarbondaleFollow

Date of Award

9-1-2020

Degree Name

Master of Science

Department

Electrical and Computer Engineering

First Advisor

Ahmed, Shaikh S.

Abstract

High electron mobility transistors (HEMTs) have long been studied for high frequency and high-power application. Among widely known high electron mobility transistors, AlGaN/GaN HEMTs are having the upper hand due to high electron mobility of the GaN channel. Over the times, issues like current collapse, gate leakage, self-heating and gate lag have questioned the performance and reliability of these devices. In the recent years, engineers have come up with newer architectures to address some of these issues. Inserting a high-k dielectric oxide layer in the gate stack proved to be an effective solution to mitigate gate leakage, reduce interfacial traps and improve optimal working conditions. This work aims to study the reliability aspect of these so-called metal-oxide-semiconductor high electron mobility transistors (MOS-HEMT) specifically, HfO2 and HfZrO2 MOS-HEMTs. It was found through numerical simulations that though HfO2 and HfZrO2 dielectrics were able to mitigate gate leakage current, they tend to accumulate more heat in the channel region with respect to the conventional silicon nitride (SiN) passivated counterparts. Moreover, few asymmetric structures were proposed where silicon nitride was placed in the dielectric layer along with HfO2/HfZrO2. In this study it was found that these asymmetric structures showed superior thermal performance while showing near-zero gate leakage current.