Magnesium Doping Controlled Density and Mobility of Two-Dimensional Electron Gas in MgₓZn₁₋ₓO/ZnO Heterostructures

The magnesium content in Mg x Zn 1- x O/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 × 10 10 cm -2 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 cm 2 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.