@Article{Ardenghi_apl_2022,
  author    = {A. Ardenghi and O. Bierwagen and A. Falkenstein and G. Hoffmann and J. Lähnemann and M. Martin and P. Mazzolini},
  journal   = {Appl. Phys. Lett.},
  title     = {Toward controllable {Si}-doping in oxide molecular beam epitaxy using a solid {SiO} source: Application to {$\beta$-Ga$_2$O$_3$}},
  year      = {2022},
  month     = {jul},
  note      = {7 pages},
  number    = {4},
  pages     = {042109},
  volume    = {121},
  abstract  = {The oxidation-related issues in controlling Si doping from the Si source material in oxide molecular beam epitaxy (MBE) is addressed by using solid SiO as an alternative source material in a conventional effusion cell. Line-of-sight quadrupole mass spectrometry of the direct SiO-flux (ΦSiO) from the source at different temperatures (TSiO) confirmed SiO molecules to sublime with an activation energy of 3.3eV. The TSiO-dependent ΦSiO was measured in vacuum before and after subjecting the source material to an O2-background of 10−5 mbar (typical oxide MBE regime). The absence of a significant ΦSiO difference indicates negligible source oxidation in molecular O2. Mounted in an oxygen plasma-assisted MBE, Si-doped β-Ga2O3 layers were grown using this source. The ΦSiO at the substrate was evaluated [from 2.9x109 cm−2s−1 (TSiO=700°C) to 5.5x1013 cm−2s−1 (TSiO=1000°C)] and Si-concentration in the β-Ga2O3 layers measured by secondary ion mass spectrometry highlighting unprecedented control of continuous Si-doping for oxide MBE, i.e., NSi from 4x1017 cm−3 (TSiO=700°C) up to 1.7x1020 cm−3 (TSiO=900°C). For a homoepitaxial β-Ga2O3 layer an Hall charge carrier concentration of 3x1019 cm−3 in line with the provided ΦSiO (TSiO=800°C) is demonstrated. No SiO-incorporation difference was found between β-Ga2O3(010) layers homoepitaxially grown at 750°C and β-Ga2O3(-201) layers heteroepitaxially grown at 550°C. The presence of activated oxygen (plasma) resulted in partial source oxidation and related decrease of doping concentration (particularly at TSiO<800°C) which has been tentatively explained with a simple model. Degassing the source at 1100°C reverted the oxidation.},
  arxiv     = {2202.05762},
  doi       = {10.1063/5.0087987},
  publisher = {{AIP} Publishing},
}