Germanium surface segregation in highly doped Ge:β-Ga2O3 grown by molecular beam epitaxy observed by synchrotron radiation hard x-ray photoelectron spectroscopy

We present a study of Ge segregation at the surface of highly germanium-doped gallium oxide (2.5 × 1020 cm−3 nominal doping level) grown by molecular beam epitaxy. We probed the dopant concentration as a function of depth by hard x-ray photoelectron spectroscopy and standard laboratory photoemission spectroscopy. We notably found that there is germanium segregation within the top 2 nm where its concentration is 3 times the nominal doping level. This increased dopant concentration leads to a threefold enhancement of surface conductivity. The results suggest a reliable method for delta doping for power electronics applications.