Schottky-barrier height tuning of NiGe/n-Ge contacts using As and P segregation

We present a systematic study of the Schottky barrier lowering induced by dopant segregation during nickel germanidation at NiGe/n-Ge(1 0 0) contacts. We used two different doping ions (As/P) and prepared two different NiGe layer thicknesses (30 nm/60 nm) at 400 °C. NiGe was found to exhibit a smooth interface to the Ge substrate and a very low specific resistance of 15.1 μΩ cm. Both doping species, As and P, segregated at the NiGe/Ge interface during germanidation due to the snowplow effect. We found the concentration of dopants at the NiGe/Ge interface increases with increasing implantation dose. From low-temperature measurements, significant lowering of the effective Schottky-barrier height from 0.72 eV at 0 K for diodes without ion implantation to 0.38 eV by P segregration was determined. With a value of only 0.19 eV, arsenic was found to be superior to P for Schottky barrier lowering.