Ni, Ir, Pd, Pt, and silver oxide Schottky contacts were fabricated on the Zn-polar face of hydrothermally grown, bulk ZnO. A relationship was found between the barrier height of the contact and the free energy of formation of its “metal” oxide. This was consistent with the dominating influence of O vacancies (VO) which tend to pin the ZnO Fermi level close to the VO (+2,0) defect level at approximately 0.7eV below the conduction band minimum. Therefore, a key goal in the fabrication of high quality Schottky contacts should be the minimization of O vacancies near the metal-ZnO interface.

Influence of Oxygen Vacancies on Schottky Contacts to ZnO. Allen, M.W., Durbin, S.M.: Applied Physics Letters, 2008, 92[12], 122110