Ovonic Threshold Switching Device Research Articles

A study on the interface between an amorphous chalcogenide and the electrode: Effect of the electrode on the characteristics of the Ovonic Threshold Switch (OTS)

We have studied the effect of the electrode material on the switching behavior of the Ovonic Threshold Switch (OTS) composed of metal/amorphous Ge60Se40/metal. The switching voltage is found to depend strongly on the electrode material, showing a much lower value (∼1.74 V) for Mo compared to that (∼5.85 V) of TiN. As the origin, the Schottky barrier and the interface trap states are examined, leading to a conclusion that the latter plays a crucial role. These results are interpreted by a picture of carrier transport at a metal/amorphous chalcogenide interface, providing an effective method to modulate the switching characteristics of the OTS device for various applications.

The effect of doping Sb on the electronic structure and the device characteristics of Ovonic Threshold Switches based on Ge-Se.

The Ovonic Threshold Switch (OTS) based on an amorphous chalcogenide material has attracted much interest as a promising candidate for a high-performance thin-film switching device enabling 3D-stacking of memory devices. In this work, we studied on the electronic structure of amorphous Sb-doped Ge0.6Se0.4 (in atomic mole fraction) film and its characteristics as to OTS devices. From the optical absorption spectroscopy measurement, the band gap (Eg) was found to decrease with increasing Sb content. In addition, as Sb content increased, the activation energy (Ea) for electrical conduction was found to decrease down to about one third of Eg from a half. As to the device characteristics, we found that the threshold switching voltage (Vth) drastically decreased with the Sb content. These results, being accountable in terms of the changes in the bonding configuration of constituent atoms as well as in the electronic structure such as the energy gap and trap states, advance an effective method of compositional adjustment to modulate Vth of an OTS device for various applications.

Effect of density of localized states on the ovonic threshold switching characteristics of the amorphous GeSe films

We investigated the effect of nitrogen (N) doping on the threshold voltage of an ovonic threshold switching device using amorphous GeSe. Using the spectroscopic ellipsometry, we found that the addition of N brought about significant changes in electronic structure of GeSe, such as the density of localized states and the band gap energy. Besides, it was observed that the characteristics of OTS devices strongly depended on the doping of N, which could be attributed to those changes in electronic structure suggesting a method to modulate the threshold voltage of the device.

Invited paper: Thin-film Ovonic threshold switch: Its operation and application in modern integrated circuits

The high current switching characteristics of the thin-film Ovonic Threshold Switch (OTS) offer unique advantages in modern applications. This paper covers the current theoretical understanding of the OTS switching process and highlights relevant material and device data. The paper discusses various modern applications of the OTS and OTS integration as a two terminal memory select element applicable for both PCM and RRAM. Also, a novel 3 terminal OTS device is discussed as well as other OTS application as they apply to switching and logic circuits.

Transmission line protection with thin film chalcogenide glass devices

Abstract We present the theoretical analysis of a lossless transmission line excited by voltage pulses of the type associated with high altitude nuclear explosions or with lightning. The line is protected by a thin film chalcogenide glass ovonic threshold switch (OTS). The OTS is very simply modelled as a lumped parameter network, and its OFF-ON transition is represented by a time-varying resistance which is characterized by a time constant τ. The analytical solution for the voltage transients along the line considers the applied voltage pulse as a succession of narrow component pulses whose effect is computed according to the value of the time-varying reflection coefficient at the device location. The analytical solution includes the effect of multiple reflections, and it is evaluated numerically so as to determine the voltage profile along the line. We show that the OTS device is well suited for electromagnetic pulse line protection. The effects of the delay time and of the values of the OFF and ON resistances of the switch are discussed.