We observed Shubnikov-de Haas oscillation and the quantum Hall effect in a high-mobility two-dimensional electron gas in polar ZnO/Mg(x)Zn(1-x)O heterostructures grown by laser molecular beam epitaxy. The electron density could be controlled in a range of 0.7 x 10(12) to 3.7 x 10(12) per square centimeter by tuning the magnesium content in the barriers and the growth polarity. From the temperature dependence of the oscillation amplitude, the effective mass of the two-dimensional electrons was derived as 0.32 +/- 0.03 times the free electron mass. Demonstration of the quantum Hall effect in an oxide heterostructure presents the possibility of combining quantum Hall physics with the versatile functionality of metal oxides in complex heterostructures.
Articles you may be interested inRealization of In0.75Ga0.25As two-dimensional electron gas bilayer system for spintronics devices based on Rashba spin-orbit interaction J. Appl. Phys. 112, 113711 (2012); 10.1063/1.4766749 Molecular beam epitaxy of high mobility In 0.75 Ga 0.25 As for electron spin transport applications Growth-temperature optimization for low-carrier-density In 0.75 Ga 0.25 As -based high electron mobility transistors on InP Amounts of spontaneous spin splittings were estimated from low-temperature magnetoresistances in two-dimensional electron gases created at In 0.75 Ga 0.25 As/In 0.75 Al 0.25 As heterojunctions under a gate bias. Typical sheet electron densities and mobilities in the raw wafers were ϳ1.0ϫ10 12 /cm 2 and 2 -5ϫ10 5 cm 2 /V s at 1.5 K, respectively. A maximum spin-orbit coupling constant ␣ zero of ϳ30 (ϫ10 Ϫ12 eV m) was obtained for the van der Pauw sample. In gated Hall-bar samples, a decrease in the ␣ zero value with decreasing gate voltage (V g ) was first confirmed in a normal heterojunction. The main origin for such a large ␣ zero , which is a few times larger than any previously reported, was found to be a structure-dependent so-called interface contribution in the Rashba term.
Current-driven magnetization reversal in a ferromagnetic semiconductor based (Ga,Mn)As/GaAs/(Ga,Mn)As magnetic tunnel junction is demonstrated at 30 K. Magnetoresistance measurements combined with current pulse application on a rectangular 1.5 x 0.3 microm2 device revealed that magnetization switching occurs at low critical current densities of 1.1-2.2 x 10(5) A/cm2 despite the presence of spin-orbit interaction in the p-type semiconductor system. Possible mechanisms responsible for the effect are discussed.
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