SUBJECT: M.S. Thesis Presentation
BY: Jason Jones
TIME: Monday, March 2, 2015, 3:00 p.m.
PLACE: Love Building, 210
TITLE: Electro-Thermo-Mechanical Characterization of Stress Developoment in AlGaN/GaN HEMTs Under RF Operating Conditions
COMMITTEE: Dr. Samuel Graham, Chair (ME)
Dr. Suresh Sitaraman (ME)
Dr. Ting Zhu (ME)


In this work, we present a coupled electro-thermo-mechanical finite-element model for describing the development of temperature, stress, and strain profiles within AlGaN/GaN HEMTs under DC and AC power conditions for various duty cycles. It is found that bias conditions including source-to-drain voltage, source-to-gate voltage, and pulsing frequency directly contribute to the electro-thermo-mechanical response of the device, which is known to effect device performance and reliability. The model is validated by comparing numerical simulations to experimental electrical curves (Ids-Vds) and experimental strain measurements performed using scanning joule expansion microscopy (SJEM). In addition, we show how the operating conditions (bias applied and AC duty cycle) impact the thermal profiles of the device and outline how the stress in the device changes through a pulsed cycle due to the changing thermal and electrical profiles. Qualitatively, the numerical model has good agreement across a broad range of bias conditions, further validating the model as a tool to better understand device performance and reliability.