Characterization of low resistivity Ga-doped ZnO thin films on Si substrates prepared by pulsed laser deposition

Low resistivity Ga-doped ZnO (GZO) thin films were prepared on Si substrates by using pulsed laser deposition (PLD). The influences of substrate temperature and annealing temperature on microstructural, morphological, electrical, optical and photoluminescent properties of GZO films were investigated. All the GZO films exhibit a hexagonal wurtzite structure and oriented primarily along the c-axis direction, the grain size increases as substrate temperature increases or via annealing treatment. Compact, homogeneous and smooth surfaces were observed for all the GZO films. The photoluminescence spectra demonstrate that the point defects, such as oxygen vacancy, zinc interstitial and zinc vacancy, are existed in the ZnO lattice, and the crystallinity of GZO film annealed at 400 degrees C is obviously better than other samples, demonstrating that suitable annealing temperature can improve effectively crystallization of GZO films. The Hall measurement shows that the resistivity of GZO film increases when substrate temperature increases, however, it decreases distinctly after annealing. Furthermore, carrier concentration decreases and Hall mobility increases after annealing. It is found that the resistivity of GZO thin films can be reduced at suitable annealing temperature. The lowest resistivity of 1.84 x 10(-4) Omega.cm is obtained for the GZO film deposited at 400 degrees C and then annealed at 400 degrees C.