Unveiling the Significant Role of Schottky Interfaces for Threshold Voltage in Ovonic Threshold Switching

Ovonic threshold switching (OTS) is a type of volatile resistive switching primarily observed in amorphous chalcogenides. The switching process involves an abrupt transition from a high-resistance state to a low-resistance state when a voltage above a specific threshold (Vth) is applied. OTS materials serve as selectors in nonvolatile memories with 3D XPoint-type structures, in combination with phase-change materials (PCMs), which exhibit threshold-type nonvolatile resistive switching. Despite the existence of transport models that can explain the OTS behavior, the role of the metal–OTS interface has been underexplored. This study employs angle-resolved hard X-ray photoelectron spectroscopy to investigate the interfacial electronic structure of Ge–Te-based OTS materials with different metal electrodes. The results indicate that Vth varies with the work function of the contact metal because the onset voltage for impact ionization is affected by band bending at the interface. Our findings reveal that interfacial properties significantly influence OTS behavior, offering a novel method for controlling Vth. This study underscores the importance of selecting appropriate metal contacts for optimizing the performance of OTS devices.