Heterogeneous Devices and Circuits Based on 2D Semiconductors

Abstract

Two-dimensional (2D) semiconductors have been attracting interest for numerous device applications due to their layered crystal structure which allows great thickness scalability down to monolayer and ease of integration onto arbitrary substrates. A multitude of electronic properties of different 2D materials also enables the development of transistors with high-performance and high on/off ratio. Based on previous research, 2D materials can be used to create n-type or p-type MOS transistors without adding dopants. Thus, highly staggered gap heterostructures and integrated CMOS circuits can be realized by combining two different 2D semiconductors. Moreover, given the unique properties distinct from traditional 3D materials, the radiation effect on these materials are worth being studied in order to investigate the suitability as a counterpart of silicon in extreme conditions. In this dissertation, models, design, fabrication, and characterization of devices and circuits built with heterogeneous materials and structures are developed and presented. Firstly, a general background of 2D materials is introduced, including the history, atomic structure and fabrication technique. The miscellaneous electronic properties of materials are compared and the resulting applications are reviewed leading to the motivation of this dissertation. Secondly the local backgate structure for fabricating 2D MOSFETs is discussed including the fabrication process and the device characteristics. The device performance and radiation tolerance are shown. Thirdly, the fabrication of logic and memory circuits based on heterogeneous 2D materials is introduced, while the DC and AC measurements are reviewed. Fourthly, the MoTe2/SnSe2 heterostructure is reviewed along with the characterization of each material. A novel direct synthesized technique for lateral heterostructure is shown. Finally our work is summarized, and future developments are proposed for inspiration.