We report on the formation of ohmic contacts to As- doped ZnO layers using a Pt/indium tin oxide (ITO) scheme. The As- doped ZnO layer shows p-type conductivity with carrier concentrations of 5.12-9.74 x 10(16) cm(-3) when annealed at 25-400 degrees C for 1 min in nitrogen ambient. However, the ZnO layers exhibit n-type characteristics with carrier concentration ca. 10(18)-ca. 10(19) cm(-3) when annealed at 500-800 degrees C. The Pt/ITO contacts produce contact resistivities of 8.0x10(-4) - 3.5x10(-3) Omega cm(2) upon annealing at 300-600 degrees C. Possible ohmic formation mechanisms for the Pt/ITO contacts to the As- doped ZnO layers are described and discussed. (c) 2005 The Electrochemical Society.