Select Device Concepts for Crossbar Arrays

Anatomy of Ag/Hafnia‐Based Selectors with 1010 Nonlinearity

“…These applications typically require a large crossbar array of memristors, in which sneak path currents from neighboring cells during a write or read of a target cell can severely impede the proper operation of the array. Numerous access devices coupled with a memristor at each crosspoint of the array have been introduced to tackle this critical issue [14][15][16] . Among those devices, a two-terminal thinfilm-based selector may address the issue without compromising the scalability and 3D stacking capability of the memristor.…”

Engineering Tunneling Selector to Achieve High Non-linearity for 1S1R Integration

“…The high processing temperature of the transistors makes it almost impossible to be used in 3D stacked memories. So the best approach to solve the sneak path problem is to use two-terminal thin-film-based selector devices that can be scaled laterally and stacked vertically together with a memristor (Chen, 2015;Burr et al, 2016).…”

An Optically Gated Transistor Composed of Amorphous M + Ge2Se3 (M = Cu or Sn) for Accessing and Continuously Programming a Memristor

“…The use of resistive random access memory (ReRAM), also known as memristor devices, , in circuits such as cross-point arrays, spiking neural networks, or other computing applications − where a large number of these memristive memory elements need to be incorporated into the circuit has been challenging due to their resistive nature. Without proper isolation via a selector device, − each device behaves within a circuit like it is part of a resistive network. The resistive nature of these memory elements can create multiple unwanted paths of current flow in a cross-point array even when only a single element is being addressed.…”

“…They eventually sum with the desired current through the addressed memristor, giving a false reading of the addressed memristor’s state. Circuit techniques to eliminate or reduce sneak path current have included addition of a diode in the memristor device array element. , A diode in series with each memristor prevents access to a nonaddressed element because the voltage at that node remains lower than the forward voltage of the diode, preventing current flow through the memristor element. This is a reasonable approach for the case of unipolar memristor elements that can change state with the application of a single polarity electronic input signal, such as phase-change devices.…”

“…The variable resistance creates a variable voltage across the memristor due to the voltage divider and can lead to memristor device failure or a “stuck” state. Researchers have therefore been investigating alternate materials and devices to act as “selector” devices that can prevent sneak-path current in memristor arrays. , These include the ovonic threshold switch (OTS) , and other materials such as Cu-doped HfO 2 and Ag-based materials. − These selector materials are incorporated in series with the memristor and must be electrically driven to a state that allows the memristor to be either read (without perturbation) or programmed (higher or lower resistance). While the materials may vary, there are common themes among them.…”