Analysis of All-ZnO thin film p-n junctions without extrinsic doping
W.C. HSIEH1*, Q.Y. CHEN1,2, P.V. WADERKAR1,2,3, H.C. HUANG4, C.F. CHANG1, H.H. LIU1, Y.S. WANG1, Y.T. LIN1, C.W. CHANG1, J.W. CHOU1, M.J. YANG1, H.J. CHEN1, C.M. HSIAO1, H.W. SEO5, C.H. LIAO6, H.H. LIAO7, W.K. CHU2
1Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
2Department of Physics, University of Houston, Taxes, United States of America
3Department of Chemistry, University of Liverpool, Liverpool, United Kingdom
4Department of Material Science, National Sun Yat-sen University, Kaohsiung, Taiwan
5Department of Physics, University of Arkansas, Fayetteville, United States of America
6Department of Physics, ROC Military Academy, Kaohsiung, Taiwan
7Enli Technology Inc., Kaohsiung, Taiwan
* presenting author:Wan-Chen Hsieh,
N-type ZnO thin films are commonly obtained but seeking p-type ZnO is almost like questing for the Holy Grail. However, we were able to achieve p-type ZnO thin films of m- and a-orientation grown on m- and r-oriented sapphire substrates, respectively, by RF-sputtering. The all-ZnO pn junctions were formed by putting c-oriented ZnO thin films, which are largely n-type as deposited. X-ray diffraction (XRD) verified good structural perfections and Hall measurement which done by Quantum Design PPMS system also confirmed individual n- or p-type conduction mechanism for each semiconductor layer. Measured I-V curves demonstrated characteristic diode behaviors. In efforts made to understand the origin of p-type conduction, Photoluminescence (PL) spectroscopy suggests existence of free exciton, donor accept pairs, vacancies of Zinc, and oxygen interstitials. We plan to continue the understanding of electrical properties of the p-ZnO in relation to material processing and hope to perfect the material properties by first bringing the control of carrier concentration.

Keywords: ZnO, p-type, non-polar, p-n junctions, thin film