Transparent conducting Ga-doped ZnO thin films grown by reactive co-sputtering of Zn and GaAs

Transparent conducting Ga-doped ZnO films have been deposited by rf reactive magnetron co-sputtering of Zn and GaAs in Ar-O-2 mixture at a total flow rate of 30 sccm. Ga-doped ZnO films deposited with 1% GaAs target area coverage exhibit high transparency and low electrical resistivity in a narrow operational window of substrate temperature in the range of 350-400 degrees C and 3-4% O-2 in the sputtering gas mixture. The film deposited under optimized conditions contains low arsenic impurity (similar to 0.1 at.%) and exhibits similar to 80% or higher average transmittance in the visible region and electrical resistivity of similar to 9 x 10(-6) Omega-m, which corresponds to sheet resistance of 12-15 Omega/sq. The film exhibits carrier concentration similar to 7 x 10(26) m(-3) and Hall mobility similar to 10(-3) m(2) V-1 s(-1). The high carrier concentration of the film results in the appearance of plasma resonance at similar to 1400 nm followed by high reflectance at longer wavelengths and widening of the band gap to similar to 3.7 eV due to heavy doping effects. (C) 2013 Elsevier B.V. All rights reserved.