Date of Award
Summer 2025
Document Type
Open Access Thesis
Department
Electrical Engineering
First Advisor
Iftikhar Ahmad
Abstract
The advancement of compact, thermally stable, and efficient devices for deepultraviolet (DUV) detection below 254 nm is critical for solar-blind sensing, radiation monitoring, and high-power electronics. This thesis presents the growth, fabrication, and detailed optical and thermal characterization of vertically conducting β-gallium oxide (βGa₂O₃) Schottky barrier diodes (SBDs) grown on n-type 4H-Silicon Carbide (4H-SiC) substrates using metal-organic chemical vapor deposition (MOCVD).
β-Ga₂O₃ is an ultra-wide bandgap (UWBG) semiconductor (~4.8 eV) with intrinsic DUV transparency and high breakdown electric field, making it an ideal candidate for short-wavelength photodetection. However, its low thermal conductivity limits its vertical device performance. To overcome this, β-Ga₂O₃ was heteroepitaxially grown on thermally conductive 4H-SiC substrates, which provide enhanced thermal management and structural support.
Epitaxial films with a total thickness of ~0.5 μm were deposited using MOCVD, featuring a co-delta doped lower β-Ga₂O₃ layer with silicon and indium to enhance crystalline quality, and an undoped top layer to suppress leakage current and enable solarblind operation. X-ray diffraction (XRD) revealed strong (-402) β-phase orientation with reduced full width at half maximum (FWHM), while X-ray photoelectron spectroscopy (XPS) verified successful dopant incorporation and stoichiometric film growth.
Optical measurements confirmed a significant photocurrent enhancement under 254 nm UV-C illumination, with negligible response under ambient light, validating the solar-blind nature of the devices. Temperature-dependent I–V characterization demonstrated a reduction in turn-on voltage and increased forward current density in codelta doped β-Ga₂O₃ structures, indicating improved carrier transport. With rising temperature, reverse breakdown voltage declined due to enhanced thermionic emission, while reverse leakage current increased sharply beyond 125 °C, attributed to trap-assisted conduction and dislocation activation at the Ga₂O₃/4H–SiC interface. Devices maintained stable rectifying behavior up to ~150 °C, beyond which junction isolation degraded and non-ideal I–V characteristics emerged, confirming the onset of thermally activated transport mechanisms.
These findings establish vertically conducting β-Ga₂O₃/4H-SiC heterostructures as a robust platform for short-wavelength optoelectronic applications. The integration of precise doping schemes with thermal and optical evaluation provides a scalable pathway toward next-generation UWBG detectors and switches optimized for extreme environments.
Rights
© 2025, Muhammad Hassan Tahir
Recommended Citation
Tahir, M.(2025). Optical and Thermal Characterization of Vertically Conducting Β-Ga₂O₃ Diodes Grown on 4H-SIC Substrates for Short-Wavelength (<254 >NM) Detection. (Master's thesis). Retrieved from https://scholarcommons.sc.edu/etd/8549