Date of Award

2017

Document Type

Open Access Dissertation

Department

Electrical Engineering

Sub-Department

College of Engineering and Computing

First Advisor

MVS Chandrashekhar

Abstract

Power electronic semiconductor devices are critical components in next-generation power systems such as hybrid electric vehicles and smart grid power controls enabling reduction in system size, weight, and cost. Wide bandgap materials such as SiC, GaN, and diamond have been investigated to replace silicon, due to their superior material properties. Of these, 4H-SiC is considered the most viable candidate beyond 3kV due to its technological maturity, its wide band gap (3.23 eV), high breakdown field (4×106 V/cm), high thermal conductivity (5 W/cm/K) and, more importantly, its indirect bandgap.

The main contribution of my research relates to the development and investigating the methods for growing high-quality SiC homoepitaxial layers with low defect density, particularly basal plane dislocations (BPDs) which severely affects the SiC bipolar device yield in high scale environments. The first approach of eliminating BPDs was to produce high quality SiC epilayers using a novel Si precursor Tetrafluorosilane (TFS) on nearly on-axis substrates (0.5° offcut) which inherently suppress BPD formation, by identifying a unique growth regime that promotes step flow growth in a nearly on-axis surface which is considered a major challenge in SiC epitaxy. As an alternate solution to BPD elimination in the most common 4º subtsrtaes, we developed a composite growth structure to produce 100% BPD free SiC epilayers over a wide range of C/Si ratios (1 to 1.8), introducing a minimal specific on-resistance of

Final part of this work is integrating the high quality SiC epilayers for fabricating hybrid EG/SiC Schottky structures with epitaxial graphene as an in-situ high temperature metal contact grown using TFS under Argon ambience. The EG/SiC Schottky devices fabricated exhibited an excellent ideality of 1.1 and a barrier height of 0.85 eV. These EG/SiC Schottky devices were tested as photodetectors for sensing UV light owing to graphene’s transparent optical property and 4H-SiC bandgap which is in the range of UV spectrum.

With these contributions made towards increasing the material quality and yield of SiC and SiC-graphene devices, SiC can be envisioned as a versatile and reliable material for power electronics and harsh environment sensor applications in the near future.

Available for download on Wednesday, August 15, 2018

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