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 °C with air-annealing at 600 °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 67~195 cm²/V · s to 380~490 cm²/V · s while resistivity is decreased from 31~3.7 Ω·cm to 3.6~1.2 Ω·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.