Significant enhancement of magnetic anisotropy and conductivity in GaN/CrI3 van der Waals heterostructures via electrostatic doping

van der Waals magnetic heterostructures, consisting of a wide band-gap nitride semiconductor and an intrinsic ferromagnetic semiconductor, are potentially useful for low-dimensional spintronic field-effect transistors. However, there is a significant challenge. For instance, the integration often leads to a decreased Curie temperature, the magnetic anisotropy direction change, and low conductivities. Here, we employ the first-principles density-functional method to systematically investigate the electronic and magnetic properties of the $\mathrm{GaN}/{\mathrm{CrI}}_{3}$ van der Waals heterostructures under electrostatic doping. Though the easy magnetization axis of the monolayer ${\mathrm{CrI}}_{3}$ transforms from out-of-plane to in-plane direction over 0.2 electron doping per unit cell, the $\mathrm{GaN}/{\mathrm{CrI}}_{3}$ van der Waals heterostructure maintains perpendicular anisotropy under electron doping, crucial for high-density information storage. The Curie temperature of the $\mathrm{GaN}/{\mathrm{CrI}}_{3}$ van der Waals heterostructure can be enhanced under both electron and hole doping. The $\mathrm{GaN}/{\mathrm{CrI}}_{3}$ van der Waals heterostructure presents half-metallic properties and the spin-up conductivities are much larger than that of the monolayer ${\mathrm{CrI}}_{3}$ under the same electrostatic doping. Our results indicate that constructing heterostructures with ferromagnets and nonmagnetic semiconductors is an effective strategy for developing high-performance field-effect transistors.