Modification of Surface Photovoltage Response in Microcrystalline β-Ga₂O₃ Due to Remote Plasma Treatment

β-Ga₂O₃ has attracted recent attention due to potential uses in critical areas such as high-power/high frequency telecommunication devices, next generation solar cells, biological therapeutics, etc. Nano- and microcrystalline specimens are of particular interest for budding applications. Thus, there exists a need for both facile synthesis and thorough characterization of these materials. We produced β-Ga₂O₃ microcrystals with controlled morphologies via a simple bottom-up hydrothermal method: first precursor GaOOH samples were synthesized, which then underwent a subsequent calcination, leading to the final product. Surface electronic structure and charge dynamics of the obtained materials were probed via both time- and energy-dependent surface photovoltage (SPV) conducted prior to and following a remote plasma treatment (RPT). Our findings agree with theoretical predictions for sub-bandgap states and quantify the related surface charge dynamics. We also demonstrate successful modification of these states following RPT.