Phase Segregation and Transformations in Arsenic-Implanted ZnO Thin Films

Abstract

The conversion of ZnO into a p-type semiconductor remains a major challenge for its application in optoelectronic devices because up to now neither the suitable type of defects nor the possible role of secondary phase formation during doping has been clarified. Here, the implantation of arsenic into epitaxial ZnO thin films on α-Al2O3 (0001) and subsequent isothermal annealing in high vacuum are studied by particle-induced X-ray emission, X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The as-implanted ZnO:As films are single phase and exhibit a locally disordered ZnO lattice structure. Zn3As2 nanocrystals segregate at 700 °C. Because of annealing at 800 °C, α-As and α-As2O3 are formed. The study demonstrates the role of solid-state reactions and secondary phase formation for group V element doping of ZnO that is a promising route to convert this material into a p-type semiconductor.