Magnesium doping controlled density and mobility of two-dimensional electron gas in Mg_xZn_1-xO/ZnO heterostructures

The magnesium content in Mg_xZn_1-xO/ZnO heterostructures grown by molecular beam epitaxy enables the careful control of the carrier density of the two-dimensional electron system down to 5.6 × 10¹⁰ cm² while retaining a mobility of 200,000 cm ² V^-1 S^-1 when pursuing magnesium concentrations as low as x=0.0038. By selecting an optimum magnesium content (x ∼ 0.01), the mobility is enhanced to over 700,000 cm² V ^-1 S^-1 due to reduced impurity levels associated with the use of pure distilled ozone and avoiding interface roughness scattering. This control technique allows access to the coherent transport region with strong electron-electron interaction.