Mechanism of Si doping in plasma assisted MBE growth of β-Ga2O3

We report on the origin of high Si flux observed during the use of Si as a doping source in plasma assisted MBE growth of β-Ga2O3. We show on the basis of secondary ion mass spectroscopy analysis that Si flux is not limited by the vapor pressure of Si but by the formation of volatile SiO. The low sublimation energy of SiO leads to a weak dependence of the SiO flux of Si cell temperature and a strong dependence on the background oxygen pressure. Extended exposure to activated oxygen results in reduction of SiO flux due to the formation of SiO2 on the Si surface. The work reported provides key understanding for incorporating Si into future oxide-based semiconductor heterostructure and device MBE growth.