Reducing the ?-Ga2O3 Epitaxy Temperature to 240?C via Atomic Layer Plasma Processing

In this work, we report on low-temperature asgrown single-phase epitaxial beta-gallium oxide (#-Ga2O3) films on c-plane sapphire at the substrate temperature of 240 degrees C using plasma-enhanced atomic layer deposition (PEALD). The films were deposited using triethylgallium (TEG) and Ar/O2 plasma as the metal precursor and oxygen co-reactant, respectively. Growth experiments were performed with an rf-power level of 50 W. Additionally, each unit ALD cycle was followed by in situ Arplasma annealing treatment, which consisted of Ar-plasma exposure for 20 s at 250 W rf power. X-ray diffraction (XRD) of the sample on sapphire revealed epitaxial Ga2O3 film signature with the monoclinic #-phase. On the other hand, GIXRD of the samples grown on Si and glass displayed polycrystalline #-Ga2O3 films. High-resolution transmission electron microscopy (HR-TEM) confirmed the epitaxial relationship of the Ga2O3 layers grown on sapphire substrates. X-ray photoelectron spectroscopy (XPS) shed light on the chemical bonding states of pure #-Ga2O3 layers outlining the Ga-O bonding states. STEM-EDX measurements confirmed the pristine nature of the #-Ga2O3 film with carbon atomic composition falling below the tool's detection levels.