Halide-hydrogen vapor transport for growth of ZnO single crystals with controllable electrical parameters

The advantages of HCl+H2 gas mixture as a chemical vapor transport agent for ZnO single crystals growth in the closed growth chambers are shown in comparison with Cl2, HCl and H2 by the thermodynamic analysis. The influence of the growth temperature, density of HCl+H2 transport agent and undercooling were investigated experimentally on the rate of ZnO mass transport. It was shown that HCl+H2 gas mixture provides (i) a rather high growth rate (up to 1 mm per day), (ii) a minimization of wall adhesion effect and deformations during a post-growth cooling, (iii) stable and reproduced seeded growth of the void-free single crystals with controllable conductivity and charge carrier concentration varied in the range of 2–22 (Ω cm)−1 and (1–31)·1017 cm−3, respectively. The characterization by the photoluminescence spectra, the transmission spectra and the electrical properties, as well as energy spectra of stable Cl-containing defects are analyzed.