Heterogeneous Growth of ZnO Crystal on GaN/Al₂O₃ Substrate

Abstract

Hydrothermal (HT) ZnO substrates were usually used as seeds for the vapor growth of ZnO crystals. In this work, ZnO bulk crystals were grown using the relatively low-cost GaN/Al₂O₃ substrates as seeds by chemical vapor transport (CVT). With the increase of growth time, the dislocation densities in the crystal decreased from about 1×10⁶ to 6×10³ cm⁻². The carrier concentration decreased from 1.24×10¹⁹ to 1.57×10¹⁷ cm⁻³, while the carrier mobility increased from 63.8 to 179 cm²/(V·s). The optical transmittance in the VISNIR wavelength increased significantly in combination with the decreasing dislocation densities and impurity concentrations. The dislocation lines and related fast diffusion paths gradually decreased and disappeared in the late growth stage, and the crystal qualities were consequently improved. The experimental results show that the properties of as-grown ZnO crystals are comparable with bulk ZnO grown on the HT substrates to some extent. The GaN/Al₂O₃ seeds may have a potential application value in the industrial production of ZnO single crystals.

Keywords

ZnO single crystal / GaN/Al₂O₃ substrates / chemical vapor transport / heterogeneous growth

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