There is always no shortage of research into possible future...

There is always no shortage of research into possible future memory technologies. We have heard about Leti's development of a selector for Weebit's discrete ReRAM. Now it seems that it may be feasible to have memory that consists only of a selector. This article discusses the possibility, but it seems to be very early days.

https://www.eenewseurope.com/en/selector-only-memory-gains-advocates-including-sk-hynix/

A novel type of solid-state memory, the selector-only memory (SOM) or self-selecting memory (SSM), could be about to rise from the ashes of Intel’s failed 3D XPoint non-volatile memory.

IMEC, SK Hynix, Samsung and others have been publishing learned papers, blogs and lay articles on the topic, which could be adopted for use with Compute Express Link (CXL) interconnect as well as elsewhere. CXL is used for high-speed communication between the central processing units (CPUs) and device memory or accelerators within data centers and therefore is of interest due to the AI boom/bubble.

As a result SOMs or SSMs could succeed in applications where other emerging memory technologies – the various forms of metal-oxide ReRAM and phase-change memory – have failed to gain traction to date.
The selector-only-memory is likely to be based on variants of the phase-change material systems in Ovonic Threshold Selector devices (OTS) that were used in 3D XPoint memories and that are used for various ReRAM devices.
The alternative to an OTS is a transistor as a memory cell selector switch.  A transistor is a three-terminal device that takes up additional area compared with the two-terminal OTS. As a result while transistors can be used with embedded memories some form of two-terminal device is considered superior, if not necessary, for a discrete, stackable memory.

An OTS is usually a germanium-selenium diode-switch based on an electrode cross-point so it can sit under or above the memory cell being selected. The selector serves a key role in that it selects the memory cell being addressed and prevents “sneak paths” through the array that would bypass the selected cell. However, research has shown that the OTS could perform the tasks of both memory cell and selector.

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