Total Ionizing Dose Effects and Proton-Induced Displacement Damage on MoS2-Interlayer-MoS2 Tunneling Junctions

Tunneling-dominated charge transport is demonstrated in vertically stacked MoS₂/interlayer/MoS₂ heterostructures with Al₂O₃, hexagonal boron nitride (h-BN), and HfO₂ dielectrics. All devices are highly resistant to 10-keV X-ray irradiation. Only small transient changes in X-ray-induced photocurrent are observed as a result of trap creation in the thin interlayer dielectric, with rapid passivation. Samples with Al₂O₃ and h-BN interlayer dielectrics show significant increases in conduction current during proton irradiation, due to displacement-damage-induced defects that lower the effective tunnel-barrier height. Density-functional-theory calculations provide insights into the pertinent defects. Devices with HfO₂ interlayer dielectrics show great promise for use in radiation tolerant, ultimately scaled tunnel FETs.

I. Introduction

Due to their extraordinary mechanical, electrical, and optical properties, 2-D layered materials such as graphene, semiconducting molybdenum disulfide (MoS₂), and insulating hexagonal boron nitride (h-BN) have attracted tremendous research interest and exhibit great promise for future practical applications [1]–[11]. The 2-D materials can be stacked or used as stitched layers to form vertical heterostructures that will open a new realm in the next-generation nanoscale electronics [3]–[5]. MoS₂-based heterojunctions are especially interesting for highly efficient optoelectronics due to their tunable bandgap [6]–[8]. The 2-D materials are envisioned for use in sub-7-nm microelectronics technologies as critical elements of tunneling transistors within low-power, high-density integrated circuits [3]–[5]. For example, graphene-based vertical tunneling transistors have been demonstrated with h-BN as the interlayer tunneling barrier [12], [13].