Date of Award

Fall 2023

Document Type

Open Access Dissertation

Department

Electrical Engineering

First Advisor

Krishna Mandal

Abstract

In the last two decades, significant strides have been made in the epitaxial film growth of 4H-silicon carbide (4H-SiC), establishing it as a premier wide bandgap material for radiation detection application under harsh environments. This is primarily attributed to its unique combination of physical properties such as high thermal conductivity, wide bandgap, robust breakdown field, and radiation hardness. Metal/4H-SiC epitaxial layer Schottky barrier diodes (SBDs) have emerged as reliable radiation detectors for harsh environments. However, the utilization of thicker epitaxial layer devices encounters challenges due to the minimum achievable doping concentration in 4H-SiC epitaxial layers, necessitating higher bias voltages for full depletion and consequently resulting in increased leakage current. Apart from junction properties, the presence of intrinsic crystal defects such as carbon vacancies in 4H-SiC significantly impacts radiation detector performance. To mitigate these challenges, the metal-oxide-semiconductor (MOS) structure emerges as a promising solution. By introducing an insulating oxide layer in the metal-semiconductor interface, the resulting MOS structure effectively lowers leakage current and mitigates the influence of carbon vacancy defects as well. This dissertation explores various avenues to enhance the performance of 4H-SiC-based MOS radiation detectors, addressing critical challenges and offering valuable insights into optimizing their utility in harsh environments. It also explores the impact of native SiO2 layer growth conditions on the radiation detection performance of Ni/SiO2/epi-4H-SiC MOS capacitors, aiming to optimize device performance. The findings shed light on how the oxide growth conditions influence leakage current, energy resolution, and charge trapping effects. Furthermore, the study investigates the potential of thermal oxidation to reduce EH6/7 deep levels, a carbon vacancy related defect centers, in n-type 4H-SiC epitaxial layers. These results highlight the prospect of thermal oxidation in enhancing the radiation detection capabilities of n-type 4H-SiC devices. In addition to native oxide-based MOS detectors, the research explores the Ni/Y2O3/n-4HSiC MOS structure for high-resolution radiation detection, assessing device performance in terms of energy resolution, leakage current, charge transport properties, and defect structure. The outcomes demonstrate the potential of the Ni/Y2O3/n-4H-SiC heteroepitaxial structure for achieving high-resolution radiation detection with improved device performance. The experimental results revealed substantial improvement in hole transport properties and enhanced device performance in the self-biased detector configuration.

Rights

© 2024, Omerfaruk Karadvut

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