Structural and Optical Properties of Zn_(1-x)Mg_xO Thin Films Synthesized with Metal Organic Chemical Vapor Deposition

摘要

We present the structural and optical properties of Zn_(1-x)Mg_xO thin films studied using x-ray diffraction (XRD),extended x-ray absorption fine structure (EXAFS),and photoluminescence (PL) measurements.The Zn_(1-x)Mg_xO films on sapphire [0001] substrates were fabricated with metal organic chemical vapor deposition (MOCVD).The XRD measurements showed that the Zn_(1-x)Mg_xO films (x <= 0.05) had a wurtzite structure without any MgO phase and were epitaxially grown along the c-axis of the Al_2O_3 substrate.The lattice constant of the Zn_(0.95)Mg_(0.05)O film shrank by 0.023 A,compared with that of ZnO crystals.From the EXAFS measurements on the Zn_(1-x)Mg_xO films at Zn K-edge,we found a substantial amount of distortion in the bond length of Zn-Zn pairs with a small amount of Mg substitution on the Zn site.The PL measurements showed a gradual increment of the main exciton transitions from 3.36 eV (x = 0.0) to 3.57 eV (x = 0.05) at 10 K.We also observed a strong deep-level emission near 2.3 eV from the specimen with x = 0.05.