Thin Solid Films, Vol.549, 12-17, 2013
Carrier transport and photoluminescence properties of Ga-doped ZnO films grown by ion-plating and by atmospheric-pressure CVD
Ga-doped ZnO (GZO) films with carrier concentrations ranging from 5.2 x 10(17) to 2.9 x 10(20) cm(-3) were grown on r-plane sapphire substrates by atmospheric-pressure CVD (AP-CVD). The gradients of Hall mobility (mu) - temperature (T) curves (denoted by Delta mu/Delta T) for the GZO films grown by AP-CVD (CVD-GZO films) plotted as a function of carrier concentration n obey those for the GZO films deposited by ion plating with dc arc discharge (IP-GZO films). This suggests that the dominant carrier scattering mechanism limiting the carrier transport is common between the CVD-GZO and IP-GZO films at any given n. The CVD-GZO films with low n exhibited the Ga-related neutral donor bound exciton and two-electron satellite (TES) lines at low temperature. With increasing n, the above two characteristic lines shifted higher energies accompanied by broadening. The IP-GZO films exhibited two emission lines with opposite n dependences; with increasing n, one line shifted towards higher energies, whereas another line shifted towards lower energies. With an increase in n caused by the donor doping, the relaxation of the momentum-conservation law brought the remarkable changes to the PL and PLE spectra of both the IP-GZO and CVD-GZO films with n of more than 4.0 x 10(19) cm(-3) that is close to the Mott density. (C) 2013 Elsevier B. V. All rights reserved.
Keywords:Ga-doped ZnO;Ion plating with dc arc discharge;Chemical vapor deposition;Carrier transport;Photoluminescence;Photoluminescence excitation spectra