Electrical properties and Raman spectra of undoped and Al-doped ZnO thin films by metalorganic vapor phase epitaxy

Undoped and Al-doped ZnO thin films have been deposited on Si substrates using metalorganic vapor phase epitaxy at atmospheric pressure. The as-deposited ZnO films showed good crystalline character and exhibited (002) orientation with the c axis perpendicular to the substrate surface. The carrier concentration of ZnO films was found to be dependent upon the doping of Al, and varied in the range from 1019 to 1020 cm−3. The resistivity of ZnO films was in the order of magnitude of 10−3 Ωcm. The Hall mobility decreased with the doping of Al and was in the range 5–53 cm2 (V·s)−1. Raman spectra indicated the observed A1(LO) and E2(high) bands shifted towards the low-frequency side.