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 10(5) 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 degrees C to 500 degrees 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.