Lowering the Schottky barrier at the metal-semiconductor interface remains a stern challenge in the field of field-effect transistors. Herein, an in-depth investigation was conducted to explore the formation mechanism of the Schottky barrier via interlayer distance and external electric field, utilizing the first-principles approach. Attributed to the vertical asymmetric structure of B 2 P 6 , ohmic contact forms at the interface of a graphene/B 2 P 6 (001) heterostructure, and an n-type Schottky contact with a Schottky barrier of 0.51 eV forms at the interface of a graphene/B 2 P 6 (001̄) heterostructure. Furthermore, the Schottky barrier height and the contact type can be changed by adjusting the interlayer spacing or applying an electric field along the Z direction. A high carrier concentration of 4.65 × 10 13 cm -2 is obtained in the graphene/B 2 P 6 (001) heterostructure when an external electric field of 0.05 V Å -1 is applied. Verifiably, alterations in the energy band structure are attributed to the redistribution of charges at the interface. The new findings indicate that GR/B 2 P 6 heterostructures are a key candidate for next-generation Schottky field-effect transistor development.