Abstract
Germanium with its electron and hole mobility almost three and four times of those in Silicon, respectively, is now being considered as a high mobility channel to replace Si. However, the native oxides due to their poor thermal stability have been attributed to insufficient passivation of the Ge surface, which has hindered the fabrication of Ge metal oxide semiconductor field effect transistor (MOSFET). High-κ dielectrics were used to replace native Ge oxides to improve the electrical properties. In the present work, two high-κ dielectrics as Ga2O3 (Gd2O3) mixed oxide (GGO), Al2O3 grown by molecular beam epitaxy (MBE) have been deposited on a germanium substrate. The oxide/Ge interfaces were analyzed using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). By them, we have found that the native oxides can be removed with the annealing temperatures up to 400□C.The GGO and Al2O3 deposited by our multi-chamber MBE system can effectively passivate the Ge surface without forming an interfacial layer of GeO2 according to the HRTEM pictures. The robustness of the interface is the cornerstone for further device fabrication and scaling. Those oxides also show high thermal stability of oxide and interface. The leakage current density of MBE grown GGO is 2×10-9 A/cm2 with the κ value 14.5. The interface trap density calculated by the Terman method is 1x1012 cm-2eV-1 near the midgap.