Low Electron Schottky Barrier Height of NiGe/Ge Achieved by Ion Implantation After Germanidation Technique

In this letter, an extremely low electron Schottky barrier height (SBH) of NiGe/Ge contact has been experimentally demonstrated with P⁺ ion implantation after germanidation. The results show that the current characteristics of NiGe/p-Ge diode changes from ohmic to well rectifying with I_on/I_off ratio over 10⁵ and the corresponding hole barrier height increases to 0.56 eV, which indicates that a record-low electron barrier height of 0.10 eV is achieved. The remarkable Schottky barrier modulation is attributed to phosphorus segregation near the NiGe/Ge interface. In addition, the slight dependence of the SBH on drive-in annealing temperature is also observed ranging from 350 ^°C to 500 ^°C, and the wide temperature window is beneficial for the process integration of Ge MOS device. The low electron SBH achieved in this letter is very critical to reduce the source/drain resistance and may provide new ideas for the performance improvement of Ge devices, particularly for nMOSFETs.