Tuning valley-Ohmic contacts and interfacial electronic properties in valley-polarized semiconductor/Dirac semimetal heterostructures

Abstract

Understanding and modulating the contacts and valley states in valley-polarized electronic devices is essential for designing next-generation valleytronic computing and memory devices. In this work, a class of van der Waals heterostructures (vdWHs) based on the valley-polarized semiconductor GdI₂ and Dirac semimetals X (graphene, germanene, and SiGe) is designed, achieving intrinsic p-type Ohmic contacts with precise modulation of the interfacial electronic properties. Using density functional theory calculations, we reveal that X/GdI₂ vdWHs induce a significant band gap in the Dirac semimetals due to interlayer orbital hybridization. Additionally, the graphene/GdI₂ vdWH exhibits an intrinsic p-type half-valley Ohmic contact, while germanene/GdI₂ and SiGe/GdI₂ vdWHs form intrinsic p-type overall Ohmic contacts. Due to work function differences, the contact interfaces between GdI₂ and X result in a built-in electric field, as evidenced by the calculated charge density differences and electrostatic potentials. Furthermore, by adjusting the interlayer distance and applying electrostatic doping, the Schottky barrier heights and valley splitting in X/GdI₂ vdWHs can be precisely tuned, which facilitates transitions from a half-valley Ohmic contact to an overall Ohmic or Schottky contact, achieving valley-switching ON/OFF states at K and K′ points. This study provides strategies for realizing multi-state valley-polarized electronic devices through interface engineering of valley-polarized semiconductors and Dirac semimetals.