Improving electron transport in Ga-doped Zn0.7Mg0.3O, a wide-gap band-edge-energy-tunable transparent conducting oxide

The band gap increase in Zn(Mg)O alloys with increasing Mg enables tunable control of the conduction band alignment. However, the conductivity decreases monotonically with increasing Mg. Here, we show that the leading cause of the conductivity decrease is the increased formation of acceptor-like compensating intrinsic defects, such as zinc vacancies (V_Zn), which reduce the free electron concentration and decrease the mobility through ionized impurity scattering. Post-deposition annealing of Ga-doped Zn_0.7Mg_0.3O films grown by pulsed laser deposition increases the mobility by 50% due to pairing of oppositely charged defects, resulting in a conductivity as high as σ = 475 S/cm.