Comparative Study of Properties of ZnO/GaN/Al_2O_3 and ZnO/Al_2O_3 Films Grown by Low-Pressure Metal Organic Chemical Vapour Deposition

摘要

ZnO films were deposited by low-pressure metal organic chemical vapour deposition on epi-GaN/Al_2O_3 films and c-Al_2O_3 substrates. The structure and optical properties of the ZnO/GaN/Al_2O_3 and ZnO/Al_2O_3 films have been investigated to determine the differences between the two substrates. ZnO films on GaN/Al_2O_3 show very strong emission features associated with exciton transitions, just as ZnO films on Al_2O_3, while the crystalline structural qualities for ZnO films on GaN/Al_2O_3 are much better than those for ZnO films directly grown on Al_2O_3 substrates. Zn and O elements in the deposited ZnO/GaN/Al_2O_3 and ZnO/Al_2O_3 films are investigated and compared by x-ray photoelectron spectroscopy. According to the statistical results, the Zn/O ratio changes from Zn-rich for ZnO/Al_2O_3 films to O-rich for ZnO/GaN/Al_2O_3 films.