Impurity-related Charge-state Transition Levels in β-Ga2O3

Gallium sesquioxide (β-Ga2O3) is an ultra-wide band gap semiconductor (Eg ≈ 4.8 eV) which has attracted considerable attention in recent years for its potential use in power electronics and UV photo-detectors. For β-Ga2O3 to live up to its potential, the influence of impurity related defects on its electrical and optical properties needs to be better understood. Indeed, deep level transient spectroscopy (DLTS) and steady state photocapacitance spectroscopy (SSPC) show that several electrically active defect levels are present in as grown material, or may arise after irradiation or thermal treatments. For example, iron and titanium are typical impurities in bulk β-Ga2O3, and we have shown that these impurities exhibit defect levels in the upper part of the band gap, as observed by DLTS and SSPC, and also confirmed by density functional calculations. Using SSPC, it has also been possible to identify the optical signatures related to Fe and Ti. Here, we will present the status of understanding electrically active defects related to impurities in β-Ga₂O₃, and discuss recent results on defect levels arising after hydrogenation.