Formation Mechanisms of Low-Resistivity Ni/Pt Ohmic Contacts to Li-Doped p-Type ZnO

Low-resistivity Ni/Pt ohmic contacts were fabricated on Li-doped, p-type ZnO films using electron-beam evaporation, which wereconfirmed by the transmission line model technique. The current transport and formation mechanisms of the ohmic contacts wereinvestigated by X-ray photoelectron spectroscopy and temperature-dependent contact resistivity measurements. Activation ofacceptors in the ZnO films, formation of Pt–Ni solid solution near the metal surface, and forming a Zn-deficient region near theZnO surface were considered to result in the improvement of the ohmic contacts. The relatively low barrier height confirmed thatthe surface states played an important role in the formation of ohmic contacts.© 2008 The Electrochemical Society. DOI: 10.1149/1.3055337 All rights reserved.Manuscript submitted October 20, 2008; revised manuscript received December 1, 2008. Published December 18, 2008.