Synthesis of P-Type ZnO Thin Films with Arsenic Doping and Post Annealing

Abstract

We have synthesized and characterized p-type ZnO thin films doped with arsenic (As) using a spin coating method. ZnO thin films were prepared by zinc acetate dihydrate, mono-ethanol-amine (MEA), 2-methoxyethanol and As oxide, followed by post baking at 200 or 300 degrees C with air-annealing at 600 degrees C. It is confirmed that As doping converts n-type ZnO films (without As doping) to p-type films. Increasing the post baking temperature leads to a higher carrier concentration. In addition, post annealing improves crystallinity as well as carrier concentration. Mobility is enhanced from 67 similar to 195 cm(2)/V.s to 380 similar to 490 cm(2)/V.s while resistivity is decreased from 31 similar to 3.7 Omega.cm to 3.6 similar to 1.2 Omega.cm. These improvements are attributed to a larger grain size with annealing. XRD analysis shows that overall peak intensities are reduced with As doping into ZnO, which is believed that As reduces defects because it act as an acceptor.