Crystallographic Orientation Controls Contact and Spin-Photoresponse in 2D Magnetic Heterostructures.

Two-dimensional ferromagnetic semiconductors such as CrSBr offer exceptional air stability, strong magnetic anisotropy, and rich magneto-optoelectronic coupling, yet inefficient electrical contacts continue to limit carrier injection and spin transport in practical devices. Here, we show that crystallographic orientation in CrSBr/MnSBr heterojunctions provides atomic-scale control over contact type, the direction of the built-in electric field, interfacial charge transfer, and spin-dependent photocurrent. Using density functional theory and non-equilibrium Green function transport simulations, we compare lateral (x- and y-type) and vertical (z-type) interfaces. Lateral heterojunctions form low-barrier n-type or p-type Ohmic contacts through strong interfacial hybridization. In contrast, the vertical configuration yields a Schottky barrier due to weak van der Waals coupling. These orientation-dependent contacts translate directly into distinct quantum transport and rectification behaviors. Under illumination, the heterostructures exhibit strongly anisotropic, spin-polarized photocurrents with pronounced spectral selectivity: parallel magnetic configurations show a pronounced photoresponse in the infrared, while antiparallel configurations are selectively responsive in the ultraviolet. These results establish two fundamental design principles-interface dimensionality dictates Ohmic versus Schottky character and magnetic configuration controls infrared/ultraviolet spectral selectivity-unlocking a new degree of freedom for programmable spin-optoelectronic devices beyond conventional vertical heterostructures.