Influences of Orientation and Remote O₂ Plasma Exposure on the Interface Properties of SiO₂/β-Ga₂O₃ MOS Capacitors

Here we report on defect properties of atomic layer deposition (ALD) grown SiO2/ $\beta $ -Ga2O3 MOS capacitors using capacitance–voltage ( ${C} - {V}$ ), UV-assisted ${C} - {V}$ , and deep-level transient spectroscopy (DLTS). We investigated the defect properties on (100), (010), and (−201) orientations and with or without remote O2 plasma exposure before SiO2 deposition. Interestingly, only minor differences in types and total interface state densities are observed amongst these orientations. However, we find that for all orientations, remote O2 plasma exposure significantly increases the densities of fast charge states initially empty at equilibrium. Indication of mobile charges is observed at room temperature and 400 K. Thus, exposure to even remote O2 plasma causes damage to the surface of $\beta $ -Ga2O3.