Plasma-assisted epitaxial growth of ZnO layer on sapphire

Zinc oxide thin films were epitaxially grown at 400 degrees C on C-sapphire substrates by plasma-assisted epitaxy in which elemental zinc is supplied through oxygen plasma excited by radio frequency power at 13.56 MHz. The in tensity of bound exciton emission was strongly dependent on the growth rate and was drastically increased with decreasing the growth rate. Surface mor phology was also roughened with increasing the growth rate. An initial laye r grown with low growth rate around 1.7nm/min at 400 degrees C is quite eff ective in preventing the unfavorable growth and then to improve the success ive growth of a thick ZnO layer with high growth rate. Photoluminescence pr operty and surface morphology were also very much improved with suppressing poly-crystallization in this way in the thick layer grown at high growth r ate around 17 nm/min on the initial layer thicker than 300 nm. (C) 2000 Els evier Science B.V. All rights reserved.