Reduction of unintentional Si doping in β-Ga2O3 grown via plasma-assisted molecular beam epitaxy

Abstract

The authors investigate unintentional Si doping in β-Ga2O3 thin films grown via plasma-assisted molecular beam epitaxy. By identifying the Si dopant cell and the radio frequency oxygen plasma source as the two major sources of unintentional Si present in the growth chamber, adjustments to the parameters controlling these sources allow for the reduction of unintentional Si doping in β-Ga2O3 films by over two orders of magnitude. Decreasing the temperature of the Si dopant cell when idle reduces the unintentional doping from 2 × 1018 to 3 × 1017 cm−3. Furthermore, decreasing the oxygen plasma power from 300 to 250 and to 200 W results in the reduction of the unintentional Si doping from 3 × 1017 to 1 × 1016 cm−3. The reduction in unintentional Si doping concentration allows for low doping density in the drift region of β-Ga2O3 devices to design for high breakdown voltage via plasma-assisted molecular beam epitaxy.