Intrinsic Polarization-Induced Enhanced Ferromagnetism and Self-Doped p–n Junctions in CrBr₃/GaN van der Waals Heterostructures

Abstract

Two-dimensional (2D) ferromagnetic (FM) semiconductors with a high Curie temperature and tunable electronic properties are a long-term pursuing target for the development of high-performance spin-dependent optoelectronic devices. Herein, on the basis of density functional theory calculations, we report a new strategy to tune the Curie temperature and electronic structures of a ferromagnetic CrBr 3 monolayer through the formation of CrBr 3 /GaN van der Waals heterostructures. Our calculated results demonstrate that the Curie temperature and band alignment of CrBr 3 /GaN heterostructures strongly depend on the thickness and polarization direction of the GaN layer. The combination of the CrBr 3 monolayer with N-terminated GaN nanosheets leads to enhanced FM coupling via superexchange interactions between the Cr-t 2g and Cr-e g orbitals, consequently resulting in a Curie temperature of CrBr 3 of up to 67 K. Moreover, self-doped p−n junctions can be naturally formed in the heterostructures without additional modulation of external fields. The enhanced FM coupling and self-doping effect in the heterostructures are associated with the intrinsic polarization of the GaN layer that drives interfacial electron transfers from GaN to CrBr 3 . Therefore, this work not only offers an efficient scheme to boost the Curie temperature of the CrBr 3 monolayer but also opens up a new route to realize nonvolatile van der Waals p−n junctions.

GaN/MgI2 van der Waals heterostructure: a two-factor tunable photocatalyst for hydrogen evolution

“…This is because the intrinsic polarization of GaN can exacerbate the quantum stark effect, resulting in a rapid drop in the forbidden bandwidth as the GaN thickness increases, as predicted by prior simulations. 30 Fig. 1a and d show the structures of MgI 2 and hydrogenated GaN, respectively.…”

Polarization‐Induced Band‐Alignment Transition and Nonvolatile p‐n Junctions in 2D Van der Waals Heterostructures

“…The existence of intrinsic polarization in these materials leads to a build-in electrostatic field, which can be examined by their electrostatic potential distributions (EPDs). [34] Taking a trilayer GaN(0001) nanosheet as an example, its electrostatic potential (V) presents an asymmetric distribution in which the Ga-terminated vacuum level is notably higher than the N-terminated one (Figure 1c), resulting in an electrostatic potential difference (ΔV) of 5.68 eV and dipole moment of 1.63 Deby. A similar result has also been found in other 2D PSs (Figures S1-S3, Supporting Information).…”

Heteroepitaxial growth and interface band alignment in a large-mismatch CsPbI3/GaN heterojunction

“…10,11 However, the former no doubt increases the complexity of heteroepitaxy and the latter leads to the optical absorption and exciton emission of the GaN-based heterostructures confined in the short-wavelength or ultraviolet region. Hence, the exploitation of new-type GaN-based heterostructures without the limitation of lattice mismatch is strongly desired, 12–14 which is essential for the development of optoelectronic devices with broadband response and tunable charge-carrier dynamics.…”