As-Se-Ge-S and Ge-N Heterostructures for Superior OTS Performance

Abstract

To improve the voltage threshold (Vth), off-current (Ioff), and reliability of 15nm ovonic threshold switching (OTS) selectors in one-selector-one-resistor (1S1R) devices, multilayered heterostructures (HS) of AsSeGeS and GeN were studied by varying both the thickness ratio of AsSeGeS to GeN (TOTS/TGeN) and the number of GeN layers. Electrical results showed that all HS configurations had an increased Vth and Ioff stability testing up to 1011 cycles. Notably, HS devices with an increased TOTS/TGeN ratio exhibited the lowest Ioff values. Analysis revealed that the contributions to Vth were greater from thicker GeN layers than from the interfacial barriers between AsSeGeS and GeN. Raman spectroscopy further showed that the proportion of Ge bonds changed with layer thickness, with thicker GeN layers exhibiting a higher number of Ge-Ge bonds. Optimized for 1S1R operation, 15nm HS devices achieved an Ioff of 0.4nA, a Vth of 3.25V, and significantly improved Ioff cycling variance, demonstrating the potential of HS to enhance device performance.