| PhD Viva

Name of the Speaker: Ms. Sruthi M P (EE17D413)
Guide: Prof. Anjan Chakravorty
Online meeting link: https://meet.google.com/qxu-kzom-nco
Date/Time: 12th January 2024 (Friday), 3:00 PM
Title: Compact Modeling of Novel GaN HEMT Structures: Electrical to Thermal Analysis

Abstract

Silicon-based power transistors have reached a performance plateau, primarily due to the material limitations of silicon. Therefore, it is crucial to explore alternatives. Gallium Nitride (GaN) based high electron mobility transistors (HEMTs) are swiftly emerging as the preferred choice for applications demanding high frequency, high voltage, and high-temperature capabilities. In recent years, a novel approach has been proposed, featuring nanometer-scaled channels and fin-shaped structures to enhance the performance of GaN HEMTs. To effectively design circuits using these innovative devices and to make predictions about their future performance, the development of compact models becomes a necessity.

The initial phase of this work focuses on the development of a charge-based compact model for novel fin-shaped GaN HEMTs. We developed a model for side gate capacitance of fin-shaped HEMT (Fin-HEMT) and subsequently a model was developed to estimate the threshold voltage of the device. Furthermore, a model for drain current in Fin-HEMTs is derived such that it captures the 2-DEG density, 2-DEG current, gate capacitance, accumulation current and finally the total drain current of a Fin-HEMT device with any fin configuration. This is the first charge-based model proposed for drain current and gate capacitance in Fin-HEMTs.

The latter part of the work delves into an investigation of the self-heating phenomenon in GaN HEMT devices. Notably, it explores the concept of equivalent temperature within the device and how this concept can be effectively applied in compact modeling, yielding valuable insights. Accurate temperature measurement within the device is essential to ensure safe operation and comprehend device performance. Field-plate thermometry, introduced in this work, offers a novel technique for spatially profiling temperature in GaN HEMT devices. The work's concluding segment introduces a design strategy that considers cross-coupled self-heating effects and the reliability of GaN-Si hetero-integrated circuits.

The primary contribution of this work lies in providing tools in the form of physics-based compact models, temperature extraction methods, and design strategies, paving the way for informed future performance projections in a rapidly evolving GaN technology landscape.