Helicon-wave-excited-plasma sputtering epitaxy of ZnO on sapphire (0001) substrates

Abstract

A promising approach to obtain epitaxial films of oxide semiconductors was demonstrated, namely helicon-wave-excited-plasma sputtering epitaxy. Due to the surface-damage-free nature, completely a-axis-locked c(0001)-orientation ZnO epilayers were successfully grown on sapphire (0001) substrates having ultrasmooth surfaces with atomic steps. The ZnO epilayer exhibited a dominant near-band-edge photoluminescence (PL) peak at 300 K. Since the PL was considered to be due to the recombination of excitons bound to an impurity or a defect and certain tilting and twisting of the films were observed when Ar/O2 were used as sputtering gases, purification and optimization of the overall process are necessary to obtain improved epilayer qualities.