Hydroxyl-radical-assisted growth of ZnO films by remote plasma metal-organic chemical vapor deposition

The hydroxyl-radical-assisted growth of ZnO films by remote plasma-enhanced metal-organic chemical vapor deposition (RPE-MOCVD) was investigated. Plasma was generated by an RF discharge in O-2. The change of the carrier gas from N-2 to H-2 resulted in a significant increase in deposition rate. It was found from the spectroscopic characterization of light emitted by the reactor gas in the vicinity of a substrate that the effect of the carrier gas on deposition rate is related to the occurrence of OH radicals. Oxygen radicals and OH radicals, which were observed by spectroscopic measurement, promoted film growth and suppressed deep-level emissions in photoluminescence spectra. To elucidate the effects of O and OH radicals, hydrogen and helium remote plasma techniques were also used in film growth for comparison. Finally, the ZnO films fabricated by the OH radical-assisted growth were investigated by photoluminescence and X-ray diffraction (XRD) analyses. In addition, the Zn-termination effects of the sapphire substrate surface on heteroepitaxial ZnO film growth weres investigated.