Selection of non-alloyed ohmic contacts for ZnO nanostructure based devices

Abstract

Zinc oxide (ZnO) nanorods were synthesized using a simple and economic aqueous solution method on ZnO coated p-type Si substrates. Their physical properties have been examined using appropriate techniques. These investigations showed that the as-grown ZnO nanorods on ZnO/Si are single crystalline and grown along the [001] direction. These nanostructures exhibited the rms surface roughness and activation energy of ∼16.7 nm and ∼18 meV, respectively. Stable ohmic contacts are essential for reliable operation of any electronic device. To select such contacts for ZnO nanostructures, metal contacts (M = Ag, Al, In and Sn) were deposited on perfectly cleaned ZnO nanostructures (M/ZnO) using a thermal evaporation technique. From current versus voltage measurements, it is observed that at room temperature the M/ZnO structures except Al/ZnO exhibited nearly ohmic behaviour. With increasing temperature, the contact resistance of all M/ZnO structures except In/ZnO increased due to the formation of metallic bonds between metal and ZnO nanostructures. The annealing effect on M/ZnO structures was also studied, and their behaviour has been discussed and reported. © IOP Publishing Ltd.