Effects of Ion-Bombardment-Assist and High Temperature on Growth of Zinc Oxide Films by Microwave Excited High Density Plasma Enhanced Metal Organic Chemical Vapor Deposition

In this paper we describe the growth of zinc oxide (ZnO) films on a-plane sapphire substrates by plasma enhanced metal organic chemical vapor deposition (PE-MOCVD) employing microwave excited high-density plasma. In detail, we discuss the effects of ion-bombardment-assist and high temperature on structural properties, electrical properties, optical properties, impurity concentration and thermostability by X-ray diffraction (XRD), field emission scanning electron microscopy, Hall effect measurement at room temperature, photoluminescence, secondary ion mass spectrometry and thermal desorption spectroscopy. Ion-bombardment energy is controlled by the condition of radio-frequency (RF) self bias. Moderate ion-bombardment enhances crystallinity, mobility and thermostability, and reduces concentrations of carbon and hydrogen in the films. By raising the growth temperature up to 550 °C, the qualities of films are improved. High quality ZnO film was successfully grown at 550 °C, which is a relatively low temperature compared to general MOCVD. Its full width at half maximum (FWHM) of XRD (0002) rocking curve, carrier concentration and mobility are 0.12°, 5×1016/cm3, and 89 cm2/(Vs), respectively.