Tunable Electronic Properties of Graphene/g-AlN Heterostructure: The Effect of Vacancy and Strain Engineering

Abstract

The structural and electronic properties of graphene/graphene-like Aluminum Nitrides monolayer (Gr/g-AlN) heterojunction with and without vacancies are systematically investigated by first-principles calculation. The results prove that Gr/g-AlN with nitrogen-vacancy (Gr/g-AlN-VN) is energy favorable with the smallest sublayer distance and binding energy. Gr/g-AlN-VN is nonmagnetic, like that in the pristine Gr/g-AlN structure, but it is different from the situation of g-AlN-VN, where a magnetic moment of 1 μB is observed. The metallic graphene acts as an electron acceptor in the Gr/g-AlN-VN and donor in Gr/g-AlN and Gr/g-AlN-VAl contacts. Schottky barrier height Φ B , n by traditional (hybrid) functional of Gr/g-AlN, Gr/g-AlN-VAl, and Gr/g-AlN-VN are calculated as 2.35 (3.69), 2.77 (3.23), and 1.10 (0.98) eV, respectively, showing that vacancies can effectively modulate the Schottky barrier height. Additionally, the biaxial strain engineering is conducted to modulate the heterojunction contact properties. The pristine Gr/g-AlN, which is a p-type Schottky contact under strain-free condition, would transform to an n-type contact when 10% compressive strain is applied. Ohmic contact is formed under a larger tensile strain. Furthermore, 7.5% tensile strain would tune the Gr/g-AlN-VN from n-type to p-type contact. These plentiful tunable natures would provide valuable guidance in fabricating nanoelectronics devices based on Gr/g-AlN heterojunctions.

The External Electric Field-Induced Tunability of the Schottky Barrier Height in Graphene/AlN Interface: A Study by First-Principles

“…The typical Dirac-point of graphene is found to occur at the Fermi level. The conduction band minimum (CBM) of AlN rides at the point while the valence band maximum (VBM) is found at the K point, implying an indirect bandgap of 3.1 eV, which agreed well with our previous PBE calculations [ 21 ]. The projected density of states (PDOS) indicates the VBM is mainly contributed by N p orbital electrons while the CBM is contributed by N s orbital electrons.…”

“…The plane-averaged charge density difference (PCDD) between the graphene/AlN interface is represented by Equation (2) [ 19 , 21 ]: where , and are the plane-averaged charge density of the graphene/AlN interface, AlN monolayer, and graphene monolayer, respectively. As depicted in Figure 4 a, the PCDD results show the interaction and electron transfer between the AlN and graphene sublayers.…”

“…The underlying physics is due to the lack of dangling bonds at the interface as well as the weak interactions of two sublayers [ 20 ]. In recent years, more and more work on graphene-based van der Waals (vdW) heterostructures have been reported [ 21 , 22 , 23 , 24 , 25 , 26 ]. These reports prove that the intrinsic optoelectronic properties of the individual components are preserved after contacting them.…”

“…Recently, Sciuto et al have studied the graphene/bulk-AlN rather than 2D AlN heterojunction properties, and predicted that the polarity and surface reconstruction of nitride could effectively tune the Fermi-level [ 32 ]. In addition, we previously studied how biaxial strain as well as the defects would tune the electronic properties of the graphene/AlN heterojunction by first-principles calculations [ 21 ]. However, for the vdW heterojunction, modulating the SBH is an effective method to reduce the interfacial resistance.…”

Emulation of Biological Synapse Characteristics from Cu/AlN/TiN Conductive Bridge Random Access Memory

“…Recently, nitride-based resistive switching compounds, such as AlN, ZrN, HfN, NiN, and SiN, have been reported to have excellent non-volatile properties comparable to metal oxides in terms of operation speed, endurance, and retention [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. Especially, AlN is suitable for resistive switching memory owing to its high thermal conductivity and large band gap with good insulating properties [ 29 , 30 , 31 , 32 ] and could be improved by additional approaches such as the scaling, bilayer structure, and doping like oxide-based RRAM. Robust resistive switching was reported for the TiN/AlN/TiN device [ 33 ] and Pt/AlN:Cu/PT device [ 34 ] for non-volatile memory applications.…”