Ga2O3(Gd2O3) on Ge without interfacial layers: Energy-band parameters and metal oxide semiconductor devices

Ga2O3(Gd2O3) (GGO) directly deposited on Ge substrate in ultrahigh vacuum, without a passivation layer such as GeOxNy or Si, has demonstrated excellent electrical performances and thermodynamic stability. Energy-band parameters of GGO/Ge have been determined by in situ x-ray photoelectron spectroscopy in conjunction with reflection electron energy loss spectroscopy and current transport of Fowler–Nordheim tunneling. A conduction-band offset and a valence-band offset of ∼2.3 and ∼2.42 eV, respectively, have been obtained. Moreover, self-aligned Ge pMOSFETs of 1-μm-gate length using Al2O3/GGO as the gate dielectrics have shown a high drain current and a peak transconductance of 252 mA/mm, and 143 mS/mm, respectively.