Hall mobilities of Al- and Ga-doped ZnO polycrystals

This work focuses on the Hall mobilities (mu) of Al-doped ZnO (Al-ZnO) and Ga-doped ZnO (Ga-ZnO) polycrystals. Their Hall mobilities show opposite behavior as a function of the carrier concentration (n). The potential barrier of Al-ZnO is responsible for the positive dependence in the plot of mu vs. n, while the negative slope observed in Ga-ZnO suggests scattering dominated by charged defects. The near-band-edge photoluminescence (UV, 375 nm) as a function of carrier concentration shows higher photoluminescence for Ga-ZnO compared with Al-ZnO, which also implies a larger potential-barrier effect for Al-ZnO. Such a distinctive difference in the potential-barrier effect also reasonably explains the dissimilarity in the temperature dependence of the electrical resistivity of the samples, demonstrating the control of carrier transport through the potential barrier by dopant for ZnO polycrystals. (C) 2009 Elsevier B.V. All rights reserved.