09:30 〜 09:45
▲ [18a-D411-3] Using hard X-ray nanoprobe to study the emission properties of Ga2O3 films
キーワード：Pulsed Laser Deposition, XEOL, XANES
In recent years, much attention has been paid to monoclinic β-Ga2O3 as promising ultrawide bandgap (4.9 eV) semiconductors with potential applications. According to previous reports, β-Ga2O3 should be considered as an indirect bandgap semiconductor in the study of recombination or luminescent properties. Limited by the conservation of quasi-momentum, the electrons at the conduction band minimum cannot directly recombine with the holes at the valence band maximum through band-to-band mode. Instead, the electrons emit phonons, reduce energy, and are forced to participate in the transition related to exciton and defect levels. Therefore, β-Ga2O3 usually exhibits ultraviolet, blue, and green luminescence bands which are associated with self-trapped holes (STHs) and other intrinsic point defects. In this study, the Ga2O3 films grown on sapphire substrates by pulsed laser deposition (PLD) have been investigated. The influences of substrate-grown temperature on structural and optical properties have been systematically studied via X-ray nanoprobe. The hard X-ray nanoprobe provides versatile X-ray analysis techniques and higher spatial resolution. Coordination structures and emission mechanisms of Ga2O3 film can be obtained by X-ray Absorption Near-Edge Structures (XANES) and X-ray Excited Optical Luminescence (XEOL), respectively. We found a peculiar emission peak at around 417 nm in the XEOL spectrum. Blue emission may be caused by the recombination of the donor-acceptor pair (DAP) of Ga2O3, where interstitial Ga acts as donors, and Ga vacancies and Ga-O vacancy pairs act as acceptors. Especially, the emission intensity of the 417 nm peak will increase with the X-ray irradiation time. The peculiar emission behavior will be reported in detail.