The electronic properties of β-Ga2O3 [beta-Ga2O3]

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This thesis explores the electronic structure of ß-Ga2O3, the transparent conducting oxide with the widest band gap. ß-Ga2O3 single crystals were grown using chemical vapor transport (CVT) and the Czochralski method, with stoichiometry verified by energy dispersive X-ray spectroscopy (EDX). The crystal structure and lattice parameters were analyzed through X-ray diffraction, while surface morphology of (100)-planes was characterized using low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM), revealing no surface imperfections. Electrical properties, including carrier concentration, resistivity, and mobility, were assessed using the four contact Van der Pauw method and Hall effect measurements, confirming its n-type semiconductor nature. Optical measurements of undoped and doped crystals at varying temperatures indicated that the direct energy gaps decrease with increasing temperature. High-resolution angle-resolved photoelectron spectroscopy (ARPES) was employed to investigate the valence band structure, showing excellent agreement with first-principles calculations. ARPES on Sn-doped crystals revealed emission from the conduction band minimum, allowing for direct determination of the absolute band gap. Soft x-ray photoelectron spectroscopy (XPS) identified the orbital character of the filled density of states, finding three valence band groups consistent with calculations. Additionally, XPS results i