Multifunctional Two-dimensional Semiconductor Electronic Devices

New materials and device structures have been widely studied to realize high performance integrated circuits with low power consumption.van der Waals heterostructure device is formed by van der Waals forces between two-dimensional layered materials,without constrains by lattice matching and thermal expansion coefficient.The various combination of energy bands of van der Waals heterostructures provides a path for designing versatile,multifunctional electronics.Therefore,memory,high frequency and logic devices based on the two-dimensional semiconductors will play important roles in future microelectronic devices.The layered direct-bandgap semiconductor,black phosphorus（BP）,has a tunable bandgap with layer numbers.Black phosphorus is an ambipolar semiconductor with a hole-dominate transport.BP has high mobility up to 1000cm²V^-1s^-1at room temperature,and BP has anisotropic characteristics.Rhenium disulfide（ReS₂）is an n-type anisotropic semiconductor material with a bandgap of about 1.5 eV.In this thesis,van der Waals heterostructure devices are constructed to realize the multifunctional device by using the versatility of black phosphorus and rhenium disulfide.The transport mechanisms of the devices are discussed in detail,and the electrical characteristics of the devices are systematically studied.The first part of this thesis is the black phosphorus floating gate memory devices based on rigid substrates（silicon）or flexible substrates.In the black phosphorus/alumina/black phosphorus-based sandwich structure,carriers in the channel can tunnel into the floating gate by the electric field.Studies showed that the floating gate memory can achieve a high program/erase resistance ratio above 10³with 1200s retention time.The operating voltage of the memory within 15 V and the carrier injection rate exceeding 10¹⁹cm²s^-1are achieved.This can attribute to high-?dielectric used in the devices.Finally,the flexible device can be bent more than 1000 times with a strain of～1.25%,showing a good bending resistance.Secondly,the multi-terminal tunneling device based on black phosphorus/alumina/black phosphorus structure was demonstrated.Besides,the transport mechanism and electrical characteristics of the device were analyzed systematically.In this device,carriers can tunnel efficiently from the top BP layer to the bottom BP layer.Unlike a conventional tunnel diode,the tunneling carriers in this structure move in the transverse direction for the drive current.Space charge effects due to the tunneling current can deplete the carrier concentration in the top BP and then causes a great negative differential resistance（NDR）phenomenon with an extremely steep slope in transfer characteristics（less than 60 m V/dec at room temperature）.Studies showed that the device can achieve steep slope switching in the large temperature range from 360 K down to 70 K,and the body factor is only 1/10 of the thermionic limit.Finally,the lateral heterostructure device of black phosphorus/rhenium disulfide was demonstrated,and its mechanism and multi-functional applications were also exhibited.In this part of the work,the interface optimization of a back gate black phosphorus field-effect transistor with Hf La O dielectric was fabricated with performance enhancement in photodetection.On the other hand,the phosphorous oxide layer at the interface acts as a trapping layer to realize the memory function in the black phosphorous transistor.Then we established a series of energy band models to systematically analyze the transport mechanism of BP/Re S₂heterostructure,which exhibited a tunable anti-ambipolar property.As a consequence,a ternary logic inverter with nonvolatility and a tunable multi-lingual response artificial synapse was successfully demonstrated for the first time.These findings present a detailed discussion of heterostructures transport mechanisms,providing ideas for heterostructures as new functions and multifunctional electronic devices,and demonstrating the potential of two-dimensional heterostructures electronic devices in the future integrated circuits.