Date of Graduation

12-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Zhong Chen

Committee Member

Shui-Qing (Fisher) Yu

Second Committee Member

Jia Di

Third Committee Member

Yue Zhao

Keywords

High temperature, Optical isolation, Optoelectronics, Power modules, Semiconductor, Silicon carbide

Abstract

Power modules based on wide bandgap (WBG) materials enhance reliability and considerably reduce cooling requirements that lead to a significant reduction in total system cost and weight. Although these innovative properties lead power modules to higher power density, some concerns still need to be addressed to take full advantage of WBG-based modules. For example, the use of bulky transformers as a galvanic isolation system to float the high voltage gate driver limits further size reduction of the high-temperature power modules. Bulky transformers can be replaced by integrating high-temperature optocouplers to scale down power modules further and achieve disrupting performance in terms of thermal management, power efficiency, power density, operating environments, and reliability. However, regular semiconductor optoelectronic materials and devices have significant difficulty functioning in high-temperature environments. Modular integration of optoelectronic devices into high-temperature power modules is restricted due to the significant optical efficiency drop at elevated temperatures. The quantum efficiency and long-term reliability of optoelectronic devices decrease at elevated temperatures.

The motivation for this study is to develop optoelectronic devices, specifically optocouplers, that can be integrated into high-density power modules. A detailed study on optoelectronic devices at high temperature enables us to explore the possibility of scaling high-density power modules by integrating high-temperature optoelectronic devices into the power module. The primary goal of this study is to characterize and verify the high-temperature operation of optoelectronic devices, including light-emitting diodes and photodiodes based on WBG materials. The secondary goal is to identify and integrate optoelectronic devices to achieve galvanic isolation in high-density power modules working at elevated temperatures. As part of the study, a high-temperature packaging, based on low temperature co-fired ceramic (LTCC), suitable to accommodate optoelectronic devices, will also be designed and developed.

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