China University of Science and Technology implements high mobility two-dimensional electron gas in black phosphorus low-dimensional atomic crystals

China University of Science and Technology implements high mobility two-dimensional electron gas in black phosphorus low-dimensional atomic crystals

Recently, Prof. Chen Xianhui of the University of Science and Technology of China teamed up with Professor Zhang Yuanbo of the Fudan University. After the two-dimensional black phosphorus field-effect transistor was first prepared last year, he made new progress in the study of thin-film black phosphorus crystals. The system realizes high mobility two-dimensional electron gas. The related research results were published on May 18th in Nature Nanotechnology.

In May 2014, Chen Xianhui's research group cooperated with the research team of Fudan University and Zhang Yuanbo to successfully prepare a two-dimensional field effect transistor based on nanometer-thickness direct-gap elemental semiconductor material, black phosphorus (Nature Nanotech. 2014, 9 , 372-377), its leakage current modulation amplitude is on the order of 105, and the IV characteristic curve exhibits a good current saturation effect. This work has aroused widespread concern in the international academic community. Nature and Nature Nanotechnology have introduced bright spots. Black phosphorus, as a single elemental composition, has a two-dimensional layered structure, a tunable direct bandgap, and a large anisotropic semiconductor material. With its many special electrical and optical properties, it has rapidly become a research field in low-dimensional materials. Hot spot.

Recently, on the basis of the previous work, the two research groups have succeeded in increasing the quality of black phosphorus crystals by improving the growth method and using thin layer of hexagonal boron nitride (h-BN) as the substrate for the successful implementation of thin-film black phosphorus field-effect transistors. The carrier mobility continues to increase by one magnitude. At present, the Hall mobility of hole carriers and electron carriers induced by electric field at low temperature has reached 2,000 cm2 V-1 s-1 and 900 cm2 V-1 s-1, respectively, and the field effect migration of holes has been achieved. The rate is as high as 3,900 cm2 V-1 s-1 at low temperatures. After a significant increase in mobility, the phenomenon of quantum oscillation of the resistor in a strong magnetic field (the Shubnikov-Dejas oscillation) was successfully observed for the first time in the black phosphorus material. By analyzing the electron and hole convolution mass, and the relationship between quantum oscillation period and field-induced carrier density and magnetic field vector direction, it is proved that the high mobility carrier-carrying subsystem in the black phosphorus field effect transistor has obvious two-dimensional characteristics.

Relevant theoretical calculations show that the conduction path in the black phosphorus FET is confined to a narrow quantum well within 2 nm from the interface between black phosphorus and the substrate, and the majority of the carrier's spatial distribution is concentrated at two atomic layers from the interface. within. The experimental and theoretical results consistently show that there exists a two-dimensional high mobility electron gas induced by an applied electric field near the interface between the thin layer of black phosphorus and the h-BN substrate, and its optimal mobility has reached a point of application in the field of electronics. Level. This indicates that the thin layer of black phosphorus has become another kind of two-dimensional material that can be used to prepare high-mobility electronic components and has a wide application prospect.

The above research was funded by the National Natural Science Foundation of China, the National Key Basic Research Development Plan, and the Strategic Pilot B Science and Technology Special Project of the Chinese Academy of Sciences.

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