Impact of process anneals on high-k/β-Ga₂O₃ interfaces and capacitance

Gallium oxide (β-Ga₂O₃) is becoming a popular material for high power electronic devices due to its wide bandgap and ease of processing. In this work, β-Ga₂O₃ substrates received various annealing treatments before atomic layer deposition of HfO₂ and subsequent fabrication of metal–oxide–semiconductor (MOS) capacitors. Annealing of β-Ga₂O₃ with forming gas or nitrogen produced degraded capacitance–voltage (C–V) behavior compared to a β-Ga₂O₃ control sample with no annealing. A sample annealed with pure oxygen had improved C–V characteristics relative to the control sample, with a higher maximum capacitance and smaller flat-band voltage shift, indicating that oxygen annealing improved the C–V behavior. X-ray photoelectron spectroscopy also suggested a reduction in the oxygen vacancy concentration after O₂ annealing at 450 °C, which supports the improved C–V characteristics and indicates that O₂ annealing of β-Ga₂O₃ may lead to better MOS device performance.