Date of Award

Summer 2025

Document Type

Open Access Thesis

Department

Electrical Engineering

First Advisor

Iftikhar Ahmad

Abstract

This thesis highlights the critical influence of doping strategies, specifically co-delta doping with silicon (Si) and indium (In), on improving the structural quality and device performance of β-Ga₂O₃-based Schottky barrier diodes (SBDs). To achieve better thermal management, β-Ga₂O₃ thin film was grown on bulk 4H-SiC substrates using the Metal-Organic Chemical Vapor Deposition (MOCVD) technique, renowned for its precise control over composition, thickness and doping profile. The ultra-wide bandgap (UWBG), high critical breakdown field and low turn-on resistance of β-Ga₂O₃ make it a strong candidate for next-generation power electronics and short-wavelength detection in extreme environments. However, the presence of structural defects can severely degrade key device parameters such as breakdown voltage, carrier transport and thermal stability, prioritizing the importance of high crystalline quality in film growth.

In this study, a vertically conducting β-Ga₂O₃ SBD structure was realized by first depositing a Si-doped layer (5 × 10¹⁷ cm⁻³) and then a 0.25μm undoped buffer layer with a total epitaxial thickness of approximately 0.5μm. Three distinct doping approaches were systematically studied: co-delta doping with Si and In, Si delta doping alone, and continuous Si doping; each implemented under identical growth conditions to determine the effect of doping configuration on material and device characteristics. Structural and chemical characterizations were carried out using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Among these, the co-delta doping approach resulted in the narrowest full width at half maximum (FWHM) of the (-402) XRD peak (0.44°), indicating superior crystallinity. This was further supported by Raman analysis of the Ag(3) vibrational mode near 204 cm⁻¹, which showed a sharper and more intense peak under co-delta doping. XPS analysis confirmed the uniform incorporation of Si dopants and less than 1% Indium as surfactant in the co-delta doped films which is crucial for achieving stable and efficient device operation. All three devices fabricated with a 100μm contact diameter and characterized through I–V measurements exhibited high turn-on voltages due to the undoped layer. However, the co-delta-doped structure demonstrated significantly lower on-resistance and an enhanced forward current compared to its delta-doped and continuously doped counterparts. These results clearly illustrate the effectiveness of co-delta doping in optimizing UWBG semiconductor growth for high-efficiency power electronic applications.

Rights

© 2025, Nifat Jahan Nipa

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