Theoretical Study On The Design And Transport Properties Of Group-? Two-dimensional Electronic Materials

Since graphene was discovered in 2004,two-dimensional(2D)materials have received a lot of attention.In recent years,2D materials have been in the rapid development process due to its ultra-thin thickness,clean surface and good flexibility,which attracted great interest from researchers.However,graphene is difficult to apply in electronic devices because of its zero band gap.Although 2D Mo S₂ has good stability and suitable band gap,its low carrier mobility makes it hard to be competitive in high-performance transistors.In addition,due to the poor stability of 2D black phosphorus and indium selenide in the air,their intrinsic properties will be seriously degraded in practical applications.Therefore,the design and exploration of new2D electronic materials and their applications have become the key challenges in high-performance and low-power devices.Thus,this paper has carried out systematic research from the design exploration and physical property regulation of novel materials to the evaluation of device performance and structure optimization:(1)Unusual electronic transitions in 2D layered SnSb₂Te₄ driven by electronic state rehybridization.We design an ultrathick 2D semiconductor SnSb₂Te₄ with high mobility and excellent absorption coefficient.The electronic transitions of 2D SnSb₂Te₄ is contrary to the classical 2D Mo S₂.Through studying the electronic state rehybridization with charge accumulation in the interlayer region,we reveal the bilayer SnSb₂Te₄ possesses stronger light harvesting,higher mobility,and larger photocurrent.Through different methods,we demonstrate the good stability and experimental feasibility of the 2D SnSb₂Te₄.All results indicate that 2D SnSb₂Te₄ is a promising candidate for future high-performance infrared electronic and optoelectronic devices.(2)Band offsets in new BX(X=N,P,As,Sb)lateral heterostructures(LHS)based on bond-orbital theory.Based on the bond-orbital theory,we propose novel LHS(BN)_n(BX)_n(X=P,As,Sb).The direction of the interline has important influence on the LHS electronic structures.The evolution trend of electron properties of heterojunction,including band offset,band gap and energy states,is revealed by studying the properties of bond length,strength and orbital overlap.We provide a new strategy,from chemical insight,to design novel heterostructures that can be applied into a high-throughput design in the future.(3)Study on transport characteristics of short channel devices based on group 15 materials.Through the first principles coupled with the nonequilibrium Green's function(NEGF)formalism,we systematically study the electronic properties and device performance limits of monolayer As P and Bi N.By simulating the sub-10 nm FET devices,the excellent transport characteristics are demonstrated,and the competitive performance is revealed compared with the classical 2D transistor devices.In addition,the internal relationship between the carrier effective mass and the quantum transport of the device is explored with the analysis of the electronic properties.The results show that As P and Bi N can meet the requirements of ITRS standard.2D As P and Bi N materials are promising to be used in nanoscale electronic devices.(4)Modulating tunneling width and energy window for high-on-current two-dimensional tunnel field-effect transistors.By means of the DFT and NEGF methods,we develop a device architecture strategy to modify the tunneling probability of 5 nm BP TFETs with high on-state current.Benchmarking of the energy-delay product and the performance of 32-bit ALU indicates that 2D BP TFET is a promising candidate for next-generation electronics.Our findings confirm that requirements for HP applications can be realized in 2D-based TFETs,and encourage the exploration of exotic 2D materials and novel device architectures for future high-performance electronics.