Study On Optoelectronic Memory Devices Based On Two-dimensional Floating Gate Heterostructures

In recent years,Moore’s Law has been driving the development of the semiconductor industry.However,according to the International Technology Roadmap for Semiconductors（ITRS）2.0,the downward trend in chip channel widths is reaching a theoretical limit.And ITRS 2.0 emphasizes the new development trend of"more than Moore"（Mt M）,which is characterized by the integration of diverse functions such as data acquisition and information storage/processing equipment.Among them,the integration of edge devices such as sensors and actuators and data centers such as memory and computing units is one of the main ways to realize Mt M.Two-dimensional（2D）materials are considered to be a promising material for Mt M due to their lack of surface dangling bonds and almost no restriction of lattice matching.The optoelectronic memory composed of them can simultaneously realize image sensing and memory function,thereby improving the efficiency of image recognition.This paper focuses on the research on the photodetector and memory of 2D materials and the integration of these two functions.The main work and results are as follows:（1）From the perspective of energy band engineering,a self-driven photodetector device based on p-Ga Se/n-Mo Se₂ van der Waals heterojunction is proposed.It generates a built-in electric field through the asymmetric potential distribution introduced in the heterojunction.The electric field connects the built-in electric field between the metal and the semiconductor in series with the photo-generated electromotive force generated by the photovoltaic effect,which enhances the photovoltaic effect of the device and significantly improves the responsivity of the device under self-driving conditions.When V_ds is 0 and 4 V,respectively,the responsivity of the device is 0.169 and 6.81 A W^-1,and the response time is 16 and 20ms,respectively.When V_ds=0 V,a specific detectivity can reach 6.6×10¹¹Jones,and the external quantum efficiency is 39%.After applying bias voltage,a specific detectivity increases to 2.8×10¹³ Jones.This successfully demonstrates the great potential of selenide van der Waals heterojunctions for future low-power optoelectronic applications.（2）A 2D WS₂ based semi-floating gate memory with programmable rectification mode is realized,and its rectification characteristics are quasi-nonvolatile.The constructed semi-floating gate device can realize two different rectification modes of p-n junction and n⁺-n junction,and the p-n junction rectification mode has a high rectification ratio of 10⁵.semi-floating gate memory has good static and dynamic memory characteristics.The transfer curve of the device has a large memory window,and the ultra-fast memory is realized under the high-speed gate voltage pulse of-3 V for 100 ns and 3 V for 80 ns.Semi-floating gate memory also has good photoelectric memory performance,and the device achieves photoelectric quasi-non-volatile memory for more than 40 seconds within a response time of less than 1 second.The sensing and memory functions of a single pixel are initially realized.（3）WS₂ floating gate（FG）memory with super data retention capability is realized.The device has two dynamic memory modes,namely,the writing of data"1"can be completed under the gate pulse voltage of 22 V for 1 s（mode A）and-19 V for 1 s（mode B）,the device can complete the data set to"0"under the control gate voltage pulse of 1 V 1 s.When using mode B to test the data retention capability of the memory,the memory shows very stable I_ds within 10000 s after erasing and writing data,showing super data retention capability.When the memory is tested for high-speed storage,the device can complete the writing and erasing of data"1"at gate pulse voltages of-9.5 V for 1.5μs and 2 V for 1.5μs,respectively.In the endurance test of the memory,the device can still complete the dynamic data memory work normally after completing 200 high-speed writing and erasing cycles.This research provides a reference for the next generation of high-speed quasi-nonvolatile WS₂ FG memory devices.