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Electrical properties of modulation-doped rf-sputtered polycrystalline MgZnO/ZnO heterostructures

Modulation doping effect is studied in large-area rf-sputtered polycrystalline MgZnO/ZnO heterostructures. Both polarization effect at the MgZnO/ZnO interface and carrier transferring from the modulation doping layer contribute to the improvement of electrical conductivity of the heterostructure. Modulation doping provides greater enhancement in electrical properties when Mg content in the barrier layer is lower. Temperature-independent carrier concentration is observed in low-temperature Hall measurement, indicating the existence of two-dimensional electron gas in the modulation-doped polycrystalline MgZnO/ZnO structure. The slight drop in mobility at low temperatures is caused mainly by the roughness scattering and impurity scattering.