MOVPE growth of ZnO using various oxygen precursors

Abstract

The II–VI compound semiconductor ZnO is already widely used for various applications such as UV resistive coatings, gas sensors and surface acoustic wave devices. Recently, the optoelectronic properties of ZnO are attracting increasing interest, which has been initiated by first reports on p-type doping. ZnO appears especially favorable for such applications because of its large exciton binding energy of about 60 meV, its low-power thresholds for optical pumping at room temperature and the availability of bulk ZnO substrates. Here, we report on the metal-organic vapor phase epitaxy growth of ZnO layers using diethylzinc as the zinc source and iso-propanol or tertiary-butanol as the oxygen precursors. The choice of an appropriate oxygen precursor is of great importance to minimize parasitic prereactions in the gas phase, that have a negative influence on layer quality. Epitaxial growth is conducted in a water-cooled, RF-heated horizontal quartz glass reactor. Growth rates up to 2.6 μm have been accomplished. The influence of the growth parameters as substrate temperature, reactor pressure, gas flow rates, and especially the impact of the II/VI-ratio on growth rates and quality of the epitaxial material will be discussed.