Fabrication of low resistivity p-type ZnO thin films by implanting N+ ions

Abstract

Transparent and conductive oxide films have been extensively researched in recent years for the breadth of their optically technological applications. The growth of high quality n-type ZnO films can be easily realized. One of the big challenges is the difficultly of achieving low resistivity p-type conduction for ZnO thin films. In this work, we prepared the p-type ZnO films by r.f. reactive magnetron sputtering following by N+ ions implantation and subsequent annealing in a vacuum to achieve low resistivity conductive thin films. The structural, electrical and optical properties were examined by X-ray diffraction, UV-visible, and Hall-effect measurements. The experimental results show that the films have proud (002) preferred orientation. The second phase Zn3N2 diffraction peak doesn't appear in ZnO thin films. All of the zinc oxide films show good transmittance in the range of 500–550 nm. The average transmittance in the visible spectrum can be above 80% in this study. The optical energy gap increases with increasing the amount of N+ ions implanted. The maximum value of the optical energy gap gained in this study is 3.30 eV when the implanted amount of N+ ions was 5×1017 cm-2. To study the electrical stability, the p-type ZnO films were measured again after 30 days aging at room temperature. The film still kept p-type conduction without any obvious degradation of electric conduction. The resistivity of p-type ZnO obtained in this study varied from 1.05×10-1 to 9.80×10-1 ohm-cm.