Influence of oxygen vacancies on Schottky contacts to ZnO

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 is consistent with the dominating influence of oxygen vacancies (V(O)) which tend to pin the ZnO Fermi level close to the V(O) (+2,0) defect level at approximately 0.7 eV below the conduction band minimum. Therefore, a key goal in the fabrication of high quality Schottky contacts should be the minimization of oxygen vacancies near the metal-ZnO interface. (c) 2008 American Institute of Physics.