Low-temperature growth of high quality homoepitaxial ZnO is realized by using hydrogen irradiation and annealing processes (modified method). By modified method, two-dimensional growth and atomically smooth surface with steps (terrace length similar to 75 nm) are achieved at 400 degrees C. Furthermore, FWHMs of high resolution X-ray rocking curves for (0 0 0 2) and (10-11) reflections are evaluated as narrow as 21 arcsec, which indicates that high crystallinity of the ZnO grown at 400 degrees C by modified method is almost similar to that grown at 600 degrees C by conventional method. Photoluminescence results show the considerable improvement of optical properties, such as an emersion of free exciton (FX) and a decrease of donor bound exciton (D degrees X) linewidth, by using modified method, even at growth temperature as low as 400 degrees C. (c) 2007 Elsevier B.V. All rights reserved.