Step-flow growth of homoepitaxial ZnO thin layers by halide vapor phase epitaxy using ZnCl_2 and H_2O source gases

摘要

The surface morphology of homoepitaxial (0001)ZnO thin layers grown by halide vapor phase epitaxy (HVPE) using ZnCl_2 and H_2O source gases was investigated. Atomic force microscopy (AFM) observations showed that high temperature growth at 1000 ℃ with a low input H_2O/ZnCl_2 (VI/II) partial pressure ratio of 20 strongly promoted step-flow growth. X-ray diffraction (XRD) analyses revealed the crystalline quality of the homoepitaxial ZnO layer grown at 1000 ℃ with input VI/II ratio of 20 is comparable to that of bulk ZnO substrates. Under a constant input partial pressure of ZnCl_2, the growth rate of ZnO is constant within the temperature range 700-900 ℃, and the growth rate decreases above 900 ℃ due to the shift of thermodynamic equilibrium of the growth reaction.