High-performance ZnO/ZnMgO field-effect transistors using a hetero-metal-insulator-semiconductor structure

The authors propose a new structure of ZnO/ZnMgO field-effect transistors (FETs) for demonstrating high-performance capability of ZnO-based FETs. A very thin (2 nm) ZnMgO cap layer is used for forming a hetero-metal-insulator-semiconductor (hetero-MIS) gate structure together with a 50-nm-thick Al2O3 gate dielectric. The 1-mu m-gate device showed a complete FET operation and an extrinsic transconductance of as high as 28 mS/mm and an effective mobility of 62 cm(2)/V s. The high effective mobility maintained down to such a short channel device is likely due to the use of the hetero-MIS structure, demonstrating the high-performance capability of ZnO-based FETs.