Properties of Metal Surface Barriers on High Purity Germanium

Measurements of the Schottky barrier heights formed by evaporating various metals onto etched slices of n type Ge show that the barrier height and the reverse leakage current depend on the metal work function. The results are consistent with a surface state density on the Ge ≥ 5 × 1013/cm2·eV. Only metals with work functions > 4.4 eV give acceptably small reverse currents at 80 K. Of these, evaporated Ni or Pd are judged to be best for spectrometers.