Enhancement of two-dimensional electron-gas properties by Zn polar ZnMgO/MgO/ZnO structure grown by radical-source laser molecular beam epitaxy

Abstract

A Zn polar ZnMgO/MgO/ZnO structure with low Mg composition Zn1-xMgxO layer (x = 0.05) grown on a-plane (11-20) sapphire by radical-source laser molecular beam epitaxy was reported. The insertion of a thin (1 nm) MgO layer between ZnMgO and ZnO layers in the ZnMgO/ZnO 2DEG structures results in an increase of 2DEG sheet density and affects electron mobility slightly. The carrier concentration reached a value as high as 1.1 × 1013 cm-2, which was confirmed by C-V measurements. A high Hall mobility of 3090 cm2/Vs at 10 K and 332 cm2/Vs at RT was observed from Zn0.95Mg0.05O/MgO/ZnO heterostructure. The choice of the thickness of MgO was discussed. The dependence of carrier sheet density of 2DEG on ZnMgO layer thickness was calculated in theory and the theoretical prediction and experimental results agreed well.