Band-Offset Degradation in van der Waals Heterojunctions

van der Waals heterojunctions based on two-dimensional materials are attractive for tunnel field-effect transistors, but their atomically clean and electronically sharp junction interfaces fail to realize satisfactory tunneling behavior. This work reveals the phenomenon of band offset degradation in these heterojunctions, induced by interlayer charge transfer, which can impede the band-alignment configuration that is key to turning on such devices. These discoveries help to explain the calculated deviations in heterojunction band alignment, and should be highlighted in tunnel-device exploration.