PULSED LASER DEPOSITION AND CHARACTERIZATION OF LANTHANUM-DOPED CALCIUM STANNATE EPITAXIAL THIN FILMS FOR ULTRA-WIDE BANDGAP OXIDE SEMICONDUCTOR APPLICATIONS

Abstract

CaSnO3 exists as an ultra-wide bandgap (UWBG) semiconductor with a bandgap of 4.1eV-4.4eV, which, when engineered correctly, can be advantageously used as a material for transparent thin film transistors (TFTs) or for high-power electronic applications. CaSnO3 has been regarded as an “undopable” material, due to the challenges of incorporating dopants in its perovskite structure, and the complex mechanisms that can govern the doping behavior. While there have been improvements made regarding its thin film synthesis with molecular beam epitaxy (MBE), the literature for doped thin films of CaSnO3 deposited by pulsed laser deposition (PLD) is limited and attempts to properly dope the compound have been unsuccessful. In this study, the ability to dope and grow epitaxial thin films via PLD is challenged by undertaking an extensive investigation of powder preparation routes, sintering methodologies, and thin film growth condition optimization. While no semiconducting behavior was apparent, multiple doping levels were examined, evaluating phase purity, structure deviation from bulk references, and dopant incorporation. Epitaxial thin films were deposited under varying background oxygen pressures and substrate temperatures to optimize crystalline quality. Analysis using x-ray diffraction demonstrated promise in the potential of PLD as a viable route for fabricating doped UWBG CaSnO3.