Morphological, electrical and optical properties of highly oriented undoped and doped zinc oxide and cadmium oxide films grown by atmospheric-pressure chemical vapor deposition
Morphological, electrical and optical properties of highly oriented undoped and doped zinc oxide and cadmium oxide films grown by atmospheric-pressure chemical vapor deposition
复制标题
DOI：
10.1016/j.surfcoat.2013.06.015
复制
发表时间：
2013-09
影响因子：
5.4
通讯作者：
T. Terasako;Y. Ogura;K. Ohmae;S. Fujimoto;M. Yagi;S. Shirakata
中科院分区：
文献类型：
--
作者：
T. Terasako;Y. Ogura;K. Ohmae;S. Fujimoto;M. Yagi;S. Shirakata
Morphological, electrical and optical properties of undoped and Ga-doped ZnO and undoped CdO films grown on sapphire (Al2O3) substrates by the atmospheric-pressure CVD method using Zn, Cd, H2O and GaCl3as source materials were investigated. The influences of the deviation from the stoichiometric composition were clearly observed on photoluminescence (PL), photoluminescence excitation (PLE) and photoacoustic (PA) spectra of the undoped ZnO films. The carrier concentrationnin the undoped ZnO film was found to be dominated by the hydrogen related donors rather than native defects. The Ga doping in ZnO film led to the degradation of surface flatness, the increase in carrier concentrationnand the decrease in Hall mobilityμ. With increasing carrier concentrationn, the Ga-related neutral donor bound exciton line of the Ga-doped ZnO film shifted towards shorter wavelengths, accompanied by asymmetric broadening. This is probably due to the screening of the Coulomb potential by heavily introduced donors and free-electrons. Highly oriented CdO films with smooth surfaces were successfully grown onr-Al2O3substrates. Transmittance values for the CdO/r-Al2O3films were higher than 70% in the range of 700–2500 nm. Under the assumption that the reflectance is neglected, the direct and indirect optical gap energies of the CdO films determined from the transmittance spectra were 2.34–2.38 eV and 1.98–2.06 eV, respectively. PA measurements for the CdO films revealed that the tail states associated with the residual impurities and/or the structural defects reduce the direct optical gap energy. A maximum Hall mobilityμof 178 cm2/Vs was achieved on the CdO/r-Al2O3film with the carrier concentrationnof 4.2 × 1019cm− 3.
