Acceptor Doping in Sputtered ZnO Thin Films

Acceptor doping of zinc oxide thin films prepared by radio-frequency diode sputtering, using nitrogen as a doping source, was realized during sputtering in Ar/N-2 gas mixture or via ion implantation of 180 keV N ions. Effects of N doping and (Al, Ga):N codoping on the films' properties have been studied. Highly resistive ZnO:N films with p-type carrier concentrations ranging 10(14)divided by 10(15) cm(-3) and more random orientation of the crystallites were obtained. The co-doped ZnO:Al: N and ZnO:Ga:N films maintained a c-axis texture in the direction of the surface normal. The carrier concentration of the p-type films was on the order of 10(17)divided by 10(18) cm(-3). 180 keV N ions were implanted in sputtered ZnO:Ga thin films. The implant doses varied 10(15)divided by 2x10(16) cm(-2). Annealing studies were performed under O-2 and N-2 ambient at different temperatures and times. N-implanted films were polycrystalline with a preferred caxis orientation of the crystallites. Post-implantation annealing caused the increase of the (002) diffraction line integrated area and reduction in resistivity and the biaxial stress. After annealing in N-2, a p-type conduction was observed with a carrier concentration and average transmittance on the order of 2.8x10(19) cm(-3) and 81 % respectively.