Abstract
In this study, the structural and magnetic properties of Si-doped bulk and 2D AlN were systematically investigated by first-principles calculations. Si atoms prefer to substitute Al atoms in both bulk and 2D AlN under N-rich growth conditions. In bulk AlN, Si dopants exhibit a non-magnetic state, uniform distribution, and a strong anisotropic diffusion energy barrier. In contrast to that, Si dopants prefer to form a buckling structure and exhibit a magnetic moment of 1 μB in 2D AlN. At a low Si concentration, Si atoms tend to get together with antiferromagnetic coupling between each other. However, the magnetic coupling among Si atoms changes to ferromagnetic coupling as Si concentration increases, due to the enhanced exchange splitting and delocalized impurity states. At the extreme doping limit, monolayer SiN, along with its analogs GeN and SnN, is a ferromagnetic semiconductor with a large band gap and high Curie temperature. These results indicate that 2D AlN doped by group IV atoms has potential applications in spintronic devices.
Highlights
Bridging semiconductor and magnetism is desirable to utilize charge and spin degrees of freedom simultaneously, thereby creating enhanced functionalities beyond conventional semiconductor devices [1, 2]
Diluted magnetic semiconductors (DMSs) have been realized by doping group III-V and II-VI compounds with a few percent of transition metal (TM) ions, whose magnetism arises from the ferromagnetic (FM) coupling between the electrons in the partially filled d or f orbitals [3, 4]
We examined non-equivalent Si doping sites including the substitution of an Al atom (SiAl) or a N atom (SiN), the interstitial site with z coordination between two Al [labeled as SiI,Al by Kroger–Vink notation] layers or N (SiI,N) layers (Figure 2A)
Summary
Bridging semiconductor and magnetism is desirable to utilize charge and spin degrees of freedom simultaneously, thereby creating enhanced functionalities beyond conventional semiconductor devices [1, 2]. Diluted magnetic semiconductors (DMSs) have been realized by doping group III-V and II-VI compounds with a few percent of transition metal (TM) ions, whose magnetism arises from the ferromagnetic (FM) coupling between the electrons in the partially filled d or f orbitals [3, 4]. The band gap of 2D AlN can be modulated by in-plane strain or a transverse electric field [10]. Both bulk and 2D AlN have promising applications in optics, spintronics, optoelectronics, and as substrate materials [11]. Room-temperature (RT) ferromagnetism in wurtzite AlN-based DMSs [12] has been recognized by doping transition metal (TM) dopants such as Mn [13], Cr [14], V [15], Fe [16], Co [17], Ni [18], Cu [19, 20], Zn [21], Ti [22], Ce [23], and Ag [24]. The FM coupling between TM ions was explained by various models including double exchange [13–15, 22], superexchange exchange [23], p–d hybridization [16, 20, 24], and bound magnetic polaron models [18, 19, 21]
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