Speaker
Description
Nickel-germanium (Ni-Ge) interface reactions play a crucial role in manufacturing low-resistive ohmic metal contacts on Ge. These ohmic contacts are important in applications such as Ge-based optoelectronic devices. Therefore, Ge surface oxide cleaning has been a key step in contact processing to achieve low contact resistivity. However, it has also been reported that a separate Ge oxide removal step is not necessary due to specific Ni-Ge interface reactions, which break germanium oxide bonds. Measuring these effects in Ni/Ge interfaces with laboratory XPS sources is challenging due to small chemical shifts between Ge-Ge and different Ge-Ni chemical states. In this work, we use high-resolution synchrotron-radiation photoelectron spectroscopy (SRPES) to elucidate the atomic bonding sites at Ni/Ge interfaces as a function of annealing temperature. We report the results of SRPES studies for wet chemically cleaned and native oxide containing Ni/Ge interfaces before and after ultra-high-vacuum (UHV) annealing.