Growth of Ga-doped ZnO by pulsed laser deposition at 200C in an ambient of Ar and H2 produces a resistivity of 1.5 x 10-4Ωcm, stable to 500C. The resistivity could be further reduced to 1.2 x 10-4Ωcm by annealing on Zn foil, which reduces the compensating Zn-vacancy acceptor concentration NA to 5 x 1019/cm3, only 3% of the Ga-donor concentration ND of 1.6 x 1021/cm3, with ND and NA determined from a degenerate mobility theory. The plasmon-resonance wavelength was only 1060nm, further bridging the gap between metals and semiconductors.

Stable Highly Conductive ZnO via Reduction of Zn Vacancies. Look, D.C., Droubay, T.C., Chambers, S.A.: Applied Physics Letters, 2012, 101[10], 102101