Influence of deposition conditions on the thermal stability of ZnO : Al films grown by rf magnetron sputtering

The resistivity and the thermal stability of transparent conducting ZnO lay ers doped with aluminum have been correlated with the conditions of the spu ttering process. Layers deposited at low rf power density (similar to1.3 to 2.6 W/cm(2)) exhibit a low resistivity of 9 X 10(-4) Ohm cm, predominantly due to a high concentration of intrinsic donor type defects. These donors are compensated during annealing at high temperature in a vacuum; the low r esistivity increases and the layers are not thermally stable. At rf power d ensities of similar to3.2 W/cm(2) and more, the deposition conditions yield a high growth rate and the extrinsic aluminum dopant is incorporated on va cant cation sites, These substitutional donors are thermally stable therefo re a low resistivity is retained after annealing at 550 degreesC. (C) 2001 American Vacuum Society. [DOI: 10.1116/1.1329121].