Unveiling Versatile Electronic Properties and Contact Features of Metal–Semiconductor Graphene/γ-Ge₂SSe van der Waals Heterostructures

Recently, searching for a metal-semiconductor junction (MSJ) that exhibits low-contact resistance has received tremendous consideration, as they are essential components in next-generation field-effect transistors. In this work, we design a MSJ by integrating two-dimensional (2D) graphene as the metallic electrode and 2D Janus γ-Ge₂SSe as the semiconducting channel using first-principles simulations. All the graphene/γ-Ge₂SSe MSJs are predicted to be energetically, mechanically, and thermodynamically stable, characterized by the weak van der Waals (vdW) interactions. The graphene/γ-SGe₂Se MSJ-vdWH form the <i>n</i>-type Schottky contact (SC), while the graphene/γ-SeGe₂S MSJ-vdWH form the <i>p</i>-type one, suggesting that the switching between <i>p</i>-type and <i>n</i>-type SC in the graphene/γ-Ge₂SSe MSJ-vdWHs can occur spontaneously by simply altering the stacking patterns, without requiring any external conditions. Notably, the contact features, including contact types and barriers of the graphene/γ-Ge₂SSe MSJs are significant in versatility and can be altered by applying electric gating and adjusting interlayer spacing. Both the applied electric gating and strain engineering induce switchability between <i>p</i>- and <i>n</i>-type and SC to OC in the graphene/γ-Ge₂SSE MSJs. This versatility underscores the potential of the graphene/γ-Ge₂SSe MSJ for next-generation applications that require low-contact resistance and high performance.