Determination of the band offsets of the Ga₂O₃:Si/FTO heterojunction for current spreading applications

Because of the relatively low electron mobility of Ga₂O₃, it is important to identify suitable current spreading materials. Fluorine-doped SnO₂ (FTO) offers superior properties to those of indium tin oxide (ITO), including higher thermal stability, a larger bandgap, and lower cost. However, the Ga₂O₃:Si/FTO heterojunction, including the important band offsets and the I–V characteristics, have not previously been reported. In this work, we have grown a Ga₂O_3:Si/FTO heterojunction and performed x-ray photoelectron spectroscopy measurements. The conduction and valence band offsets were determined to be 0.11 and 0.42 eV, indicating a minor barrier for electron transport and a type-I heterojunction. The subsequent I–V measurement of the Ga₂O_3:Si/FTO heterojunction exhibited pseudo-ohmic behavior. The results of this work support the potential of FTO for the current spreading layers of Ga₂O₃ devices for high temperature and ultraviolet applications. (paper)