Orientation Relationships of Zinc Oxide on Sapphire in Heteroepitaxial Chemical Vapor Deposition

The anisotropy in ZnO heteroepitaxial growth by CVD is studied on spherical and lens-shaped sapphire substrates. The layers of ZnO form maps containing many regions of single-crystals of various orientations. By combining equivalent types of these regions, six different modes in the orientation relationships between ZnO and sapphire are distinguished and classified. The effects of growth temperature and reaction gas velocity on the kinds and the extent of these regions are also investigated. The results, drawn by stereographic projection, may provide a useful guide for selecting and preparing substrate planes to obtain specific ZnO planes of high quality, i.e. smooth surface, high perfection, high electron mobility etc.

Chemically vapour deposited silicon on sapphire (SOS) films 0.25 μm thick were implanted with 28Si+ and recrystallized in solid phase by furnace annealing (FA) and IR rapid thermal annealing (RTA) in the laboratory. An improvement in crystalline quality can be obtained using both annealing procedures. After FA, it is hard to retain the intrinsic high resistivity value (104–105 Ω cm) observed in as-grown SOS films, so the improvement process cannot be put to practical use effectively. However, it is demonstrated that by properly adjusting the implantation and RTA conditions, significant improvements in both film quality and film autodoping can be accomplished. This work describes a modified double solid phase epitaxy process in which the intrinsic high resistivities of the as-grown SOS films are retained. The mechanism of suppression of Al autodoping is discussed.


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