Electrical and Structural Properties of Ti/Au Ohmic Contacts to n-ZnO

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Abstract
We have investigated Ti/Au (30/50 nm) ohmic contacts to n­ZnO:Al.n­ZnO:Al. The samples are annealed at temperatures of 300 and 500°C for 60 s in a flowing N2N2 atmosphere. Current-voltage measurements show that the as-deposited sample is ohmic with a specific contact resistance of 2×10−2 Ω cm2.2×10−2 Ω cm2. However, annealing of the sample at 300°C results in much better ohmic behavior with a contact resistance of 2×10−42×10−4 Ω cm2.Ω cm2. Further increase in annealing temperature (500°C) causes the degradation of the ohmic property. Glancing angle X-ray diffraction and Auger electron spectroscopy are used to investigate interfacial reactions between the Ti/Au and ZnO layers. It is shown that both rutile and srilankite TiO2TiO2 phases are formed in the as-deposited and annealed samples. It is further shown that annealing at 500°C results in the formation of new phases such as Ti3AuTi3Au and TiAu2.TiAu2. A possible explanation is given to describe the annealing temperature dependence of the specific contact resistance. © 2001 The Electrochemical Society. All rights reserved.