CMOS Digital Circuit Based On Two-dimensional Transition Metal Dichalcogenide Transistors

With the rapid development of the integrated circuit industry,the feature size of silicon-based integrated circuits almost reaching their physical limits.To solve this problem,researchers are committed to finding new solutions in recent years.Some of them come up with the introduction of extreme ultraviolet lithography(EUV)technology to improve production efficiency and electrical performance of the transistor.Others suggest to optimize the structure of transistors,silicon on insulator(SOI)device are recommended in order to reduce power loss caused by the leakage.In addition,twodimensional(2D)materials have attracted attention due to their extremely high carrier mobility and extremely thin atomic layer thickness.Researchers believe that twodimensional materials will replace silicon as candidates for the next generation of semiconductors.Under this condition,the combinational logic circuits based on 2D material transistors are simulated in this paper.The influences of device parameters of 2D material transistors on the output curve of the combinational logic circuits are also explored.Besides,the low-power structure of these combinational logic circuits are also studied in this paper.The main innovations and work are as follows:(1)The output characteristics of CMOS inverter based on 2D material transistors are simulated.The effect of the device parameters of 2D material transistors on the output characteristic curve is analyzed.Based on the analysis results of CMOS inverters,the output characteristics of NAND,NOR,XOR,and XOR based on 2D material transistors are also studied.From the simulation results of the CMOS inverter,we can know that when the channel widths of the P-type and N-type transistors of the CMOS inverter are equal,the switching threshold of the CMOS inverter is half of the supply voltage,the gate oxide thickness and the gate oxide material have little influence on the switching threshold.When the gate oxide thickness increases from 2.8 nm to 56 nm,the switching thresholds of CMOS inverters change within 0.2% of the supply voltage.The noise margin of CMOS inverter will gradually decrease with the increase of the gate oxide thickness of the transistor.When the gate oxide thickness reaches 35 nm,gate oxide thickness has little influence on the noise margin of the CMOS inverter.Based on the research on inverters,CMOS NAND,NOR,XOR,and XNOR gates based on 2D material transistors are also studied.The gate oxide thickness is set at 2.8 nm,and Hf O2 is used as gate oxide material of the transistors in these circuits.It can be concluded from the simulation results that the output of these combinational logic circuits corresponds to their truth table well,and their output characteristic curves are similar to the output characteristic curves of silicon-based semiconductor circuits.Those results proved that 2D materials can be used to replace silicon in circuit design.(2)The power consumption of combinational logic circuits based on 2D material transistors is studied,and three power-gating circuits are designed to reduce the power consumption.Three low-power circuit structures are designed for CMOS inverters,NAND,and XOR gate.From simulation results,it is found that under normal work conditions,the structure of self-biasing resistors control power-gating circuits is most effective.For CMOS inverters,NAND,and XOR,this structure can reduce their power consumption by 9.80%,12.53%,and 16.97%,respectively.In addition,the external signal control power-gating circuit can turn itself off when the circuit is idle,which can effectively reduce the power consumption by more than 60%.During normal working mode,this structure can also reduce the power consumption by 7.10%,7.66%,and 12.17% for the CMOS inverter,NAND gates,and XOR gate.Therefore,the external signal control power-gating circuit has more advantages in low power circuits design.(3)The one bit half-adder based on 2D material transistor is simulated,the feasibility of 2D material transistors forming an operation circuit is verified.For futher research on the CMOS inverter,Schmitt trigger based on 2D material transistor is also studied.Through the simulation results,the output result of the half-adder based on 2D material transistors conform to its truth table.It is confirmed that the basic combinational logic circuits based on 2D material transistors can be used to realize the operation circuits.From the simulation results of the Schmitt trigger,it can be concluded that for a Schmitt trigger based on 2D material transistors,when the gate oxide thickness of the transistor is 2.8 nm,and Hf O2 is used as the gate oxide material,Schmitt trigger has the strongest anti-noise ability.In addition,when the supply power decreases,the anti-noise ability of the Schmitt trigger gradually decreases.