A novel approach to enhancing performance and endurance in GeS2 OTS devices using amorphous carbon doped W2N electrodes

Three–dimensional (3D) cross-point (X–point) memory has gathered interest for its fast data processing and high density, achieved by stacking memory with a selector device to prevent misinterpretation. Ovonic threshold switching (OTS) is a promising selector due to its reversible switching behavior. Although, OTS devices typically employ transition metal nitrides (TMN) such as TiN x , TaN x , and WN x for electrodes owing to their good stability, high melting points, and low resistivity, TMNs can diffuse and degrade device performance by recrystallizing with chalcogenide alloys. Amorphous carbon (a–C) can be a good alternative electrode material due to its low roughness, cost–effectiveness, high work function (WF), and excellent thermal stability. However, the high resistivity of a–C (∼ 150 mΩ–cm) increases threshold voltage ( V th ), causing high power consumption. Therefore, combining both a–C and TMN materials can effectively obtain their advantages. This study explores the effect of varying a–C content in W 2 N electrodes on GeS 2 –based OTS selectors. The (W 2 N) 1-x C x (0 ≤ x ≤ 0.25) electrodes were deposited using DC magnetron co–sputtering. The phase of (W 2 N) 1-x C x (0 ≤ x ≤ 0.25) films transformed from polycrystalline to amorphous with increasing x. Devices with (W 2 N) 1-x C x /GeS 2 /W 2 N structure showed decreased V th and off current, improving from 4.8 to 3.8 V and 8.0–4.17 nA, respectively. The subthreshold slope, distance between traps, and interface trap density ( N it ) were extracted using the Pool–Frenkel model. The reduced V th may be attributed to a higher WF and lower N it with increasing x. The device’s lifetime improved up to 1.0 × 10 9 pulses for the highest a–C content in (W 2 N) 1-x C x (0 ≤ x ≤ 0.25) electrodes. • Easy fabrication using DC–DC co–sputtering. • Innovative electrode design using a–C and W2N. • Microstructure studies of (W2N)1-xCx electrode. • Vth and Ioff reduction to minimize power consumption. • Excellent endurance of 109 pulses.