Ultrafast Non-volatile Memory Based On Direct Charge Injection

Due to the physical separation of processors and memory,computers based on von Neumann architecture exist time delays and huge energy consumption.In the past few decades,processor performance has developed rapidly in accordance with Moore's Law.In contrast,the lagging memory performance has become a huge bottleneck restricting the computing power of von Neumann computers,that is,the"Memory wall"problem.An effective measure to solve the"memory wall"problem is to develop high-speed memory devices based on new structures and new mechanisms.In recent years,floating gate memories based on new heterostructures often possess the problems such as high operating voltage,low response speed,and short retention time,which limit their compatibility in practical CMOS circuits.In order to promote the development of new high-speed memories,it is urgent to develop a memory with low operating voltage,fast response,and long storage time to expand the innovation of next-generation electronic components.In this paper,two kinds of high-speed non-volatile memories are developed through the working mechanism of direct charge injection.Firstly,we constructed an asymmetric high-speed non-volatile memory with Mo S₂/hexagonal boron nitride(h BN)/graphdiyne(GDY)/graphene structure,which is different from the working mechanism of charge tunneling in floating gate memory.Due to the direct injection of charges into graphdiyne via graphene,the device has an ultra-fast writing speed(8 ns)and an ultra-low writing voltage(30 m V).Meanwhile,benefited from the excellent charge trapping ability of graphdiyne and the band bending of graphene/graphdiyne heterostructure,the injected charges can be trapped in graphdiyne for a long time,resulting in the device with long storage time(>10~4 s).Although the above device structure processes ultra-fast writing speed and ultra-low operating voltage,the band structure of graphdiyne/graphene heterojunction is not conducive to electron injection.Thus,the erasing process of the device requires microseconds time,exhibiting asymmetric write/erase speeds.In order to achieve true high-speed non-volatile memory,we further optimized the device structure and constructed a symmetric high-speed non-volatile memory based on Mo S₂/h BN/Mo S₂/graphdiyne oxide(GDYO)/WSe₂ heterostructure.In this device,we firstly propose the working mechanism of using threshold-switching memristive material(GDYO)to control charge injection into the floating gate.Since the threshold-switching memristor can be turned on quickly at nanosecond pulse width and spontaneously turn off after the voltage is removed,the device has symmetrical write and erase speeds in nanoseconds(20 ns),low operating voltage(2 V)and ultra-long retention time(10years).Compared with the recently reported high-speed non-volatile memory based on the Fowler-Nordheim(F-N)tunneling mechanism,the operating voltage of the device is reduced by an order of magnitude,which can significantly reduce the thermal effect and energy consumption of the device,and improve the compatibility in CMOS.In addition,the device can achieve multi-level storage(3-bit)at nanosecond pulses,which may increase the data storage density of the memory.In this paper,the high-speed non-volatile memory based on the direct charge injection mechanism has the advantages of low operating voltage,fast response speed,and long storage time,which may provide a new strategy for developing the next generation of high-speed and ultra-low energy storage devices and breaking through the problem of"memory wall".