Developing high-transmittance heterojunction diodes based on NiO/TZO bilayer thin films
1 Department of Electrical Engineering, National Chung Hsing University, Taichung, 402, Taiwan
2 Department of Electronic Engineering, Kao Yuan University, Kaohsiung, 821, Taiwan
3 Department of Electrical Engineering, Cheng-Shiu University, Kaohsiung, 833, Taiwan
4 Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung, 811, Taiwan
Nanoscale Research Letters 2013, 8:206 doi:10.1186/1556-276X-8-206Published: 1 May 2013
In this study, radio frequency magnetron sputtering was used to deposit nickel oxide thin films (NiO, deposition power of 100 W) and titanium-doped zinc oxide thin films (TZO, varying deposition powers) on glass substrates to form p(NiO)-n(TZO) heterojunction diodes with high transmittance. The structural, optical, and electrical properties of the TZO and NiO thin films and NiO/TZO heterojunction devices were investigated with scanning electron microscopy, X-ray diffraction (XRD) patterns, UV-visible spectroscopy, Hall effect analysis, and current-voltage (I-V) analysis. XRD analysis showed that only the (111) diffraction peak of NiO and the (002) and (004) diffraction peaks of TZO were observable in the NiO/TZO heterojunction devices, indicating that the TZO thin films showed a good c-axis orientation perpendicular to the glass substrates. When the sputtering deposition power for the TZO thin films was 100, 125, and 150 W, the I-V characteristics confirmed that a p-n junction characteristic was successfully formed in the NiO/TZO heterojunction devices. We show that the NiO/TZO heterojunction diode was dominated by the space-charge limited current theory.