An article was published in the journal Nature in which scientists from Fudan University reported the development of the fastest flash memory in history. The prototype operates at a speed of 400 picoseconds both when writing and reading. The new memory has been given the poetic name “Dawn” (Poxiao). The prototype has a modest capacity. The conquest of volumes will begin at the next stage of development.
Image source: Nature
Scientists from China have been developing a new type of memory since 2015. In 2021, they proposed a basic theoretical model, and in 2024, they developed an ultra-fast flash memory device with a channel length of 8 nm, which exceeded the physical size limit of silicon-based flash memory, which was about 15 nm. But size is not the main thing. The main thing is the unimaginable speed of the new non-volatile cell, which turned out to be 100,000 times faster than an SRAM cell.
Scientists noted that classical memory based on controlling a transistor channel with an electromagnetic field has fundamental limitations for increasing the speed of writing and reading. Electrons need to be “accelerated” to make them move into or out of a memory cell. Traditional semiconductor materials and the effect of a field on electrons make all this slow by modern standards. By and large, little has changed since the invention of the field-effect transistor about 60 years ago. To speed things up, you literally need different physics.
Chinese scientists have proposed using graphene or a conditionally two-dimensional semiconductor — tungsten diselenide (WSe₂) — as a channel. Both materials behave similarly, although they have differences. The distribution of the control electromagnetic field along the channels is such that the electrons enter the cell “highly overheated” — with extremely high energy for them.
In general, graphene is considered a so-called Dirac material, in which electrons obey the quantum Dirac equations. The use of graphene allows for the acceleration of the movement of “hot” electrons and holes into the memory cell, minimizing energy losses. In fact, under the created conditions, the electron becomes a massless particle, which allows for a sharp increase in the write and read speeds. The work on subnanosecond flash memory enabled by 2D-enhanced hot-carrier injection can be found at this link. It is freely available for reading.
The new memory has a thin 2D channel that optimizes the horizontal electric field distribution, increasing injection efficiency. The injection current reaches 60.4 pA/μm at a voltage of 3.7 V. The new memory can withstand more than 5.5 million write and erase cycles. The write and read speeds are the same — 0.4 ns for each mode. The prototype’s volume is about 1 kilobyte. Within five years, the team promises to increase the capacity to tens of megabytes, obtain a license, and begin releasing commercial copies.