The Achievement of a Zinc Oxide-Based Homojunction Diode Using Radio Frequency Magnetron Cosputtering System

(Al + N)-codoped p-type zinc oxide (ZnO)/undoped n-type ZnO homojunction structure was deposited onto Si (100) substrate by using radio frequency (rf) magnetron cosputtering system. Transparent indium tin oxide (ITO)-ZnO cosputtered film was employed as the ohmic contact electrode to the n-type ZnO film, and the specific contact resistance was optimized to 2.9×10-6 Ω cm2 after treating by a rapid thermal annealing (RTA) process at 400°C for 5 min under vacuum ambient. The ohmic contact behavior between the metallic Ni/Au and p-ZnO film also was improved to 3.5×10-5 Ω cm2 after annealing at 300°C for 3 min under nitrogen ambient. The interfacial diffusion of these ohmic contact systems which led to the optimization of the specific contact resistances by the RTA process was investigated by the Auger electron spectroscopy (AES) depth profile measurements. The diode characteristics of the resulting p-ZnO/n-ZnO homojunction structure realized with these ohmic contact electrodes were confirmed by current-voltage (I-V) measurement, which performed a forward turn-on voltage of 1.44 V with a reverse current of 1.1×10-5 A at −2 V.