Scalable Memdiodes Exhibiting Rectification and Hysteresis for Neuromorphic Computing

TL;DR

This paper presents scalable metal-Nb₂O₅₋ₓ-metal memdiodes with rectification and hysteresis, suitable for neuromorphic computing, operating via defect-controlled transport without post-fabrication treatments.

Contribution

It introduces a defect-based conduction mechanism in Nb₂O₅₋ₓ memdiodes that enables scalable, treatment-free devices with neuromorphic functionalities.

Findings

Devices exhibit rectification and hysteresis due to charge trapping.

Turn-on voltage scales with Schottky barrier height and device thickness.

High defect density enables operation in thick devices (> 100 nm).

Abstract

Metal-Nb$_{2}$O$_{5-x}$-metal memdiodes exhibiting rectification, hysteresis, and capacitance are demonstrated for applications in neuromorphic circuitry. These devices do not require any post-fabrication treatments such as filament creation by electroforming that would impede circuit scalability. Instead these devices operate due to Poole-Frenkel defect controlled transport where the high defect density is inherent to the Nb$_{2}$O$_{5-x}$ deposition rather than post-fabrication treatments. Temperature dependent measurements reveal that the dominant trap energy is 0.22 eV suggesting it results from the oxygen deficiencies in the amorphous Nb$_{2}$O$_{5-x}$. Rectification occurs due to a transition from thermionic emission to tunneling current and is present even in thick devices (> 100 nm) due to charge trapping which controls the tunneling distance. The turn-on voltage is linearly proportional to the Schottky barrier height and, in contrast to traditional metal-insulator-metal diodes, is logarithmically proportional to the device thickness. Hysteresis in the I-V curve occurs due to the current limited filling of traps.