Influence of the deposition temperature on electronic transport and structural properties of radio frequency magnetron-sputtered Zn1-xMgxO:Al and ZnO:Al films

ZnO:Al and Zn1-xMgxO:Al films have been deposited by magnetron sputtering from ceramic targets at substrate temperatures from room temperature to 500 degrees C. We studied the relation between the electronic transport and the structural properties as a function of the deposition temperature. Films with the lowest resistivity (7.10(-4) Omega cm for ZnO:Al and 3.6.10(-3) Omega cm for Zn1-xMgxO: Al) can be prepared for deposition temperatures around 300 degrees C. This optimum is accompanied by the highest carrier concentration and the highest Hall mobility. Changes in crystalline quality and free carrier concentration are explained as a result of a bombardment of the films by high energetic negative oxygen ions during growth and by phase segregation for higher deposition temperatures. The dependence of the Hall mobility on the carrier concentration can be explained by grain barrier scattering for n <approximate to 5.10(20) cm(-3) and by ionized impurity scattering for n >approximate to 5.10(20) cm(-3). From the fit of the mu(n) dependence for both materials a trap density at grain boundaries of N-t approximate to 2.3.10(13) cm(-2) was determined.