Band structure, effective mass, and carrier mobility of few-layer h-AlN under layer and strain engineering

Abstract

Wide bandgap two-dimensional semiconductors are of paramount importance for developing van der Waals heterostructure electronics. This work reports the use of layer and strain engineering to introduce the feasibility of two-dimensional hexagonal (h)-AlN to fill the scientific and application gap. We show that such one- to five-layer h-AlN has an indirect bandgap, tunable from 2.9 eV for a monolayer to ∼3.5 eV for multilayer structures, along with isotropic effective masses and carrier mobilities between zigzag and armchair directions. With an increase in the layer number to bulk AlN, the bandgap will experience a transition from an indirect gap to direct gap. Surprisingly, high room-temperature mobilities of electrons and holes (of the order of 1000 cm2 V−1 s−1) in a relaxed monolayer h-AlN system and widely adjustable effective masses and carrier mobilities in a different layer h-AlN are observed. In the presence of strain engineering, the bandgap decreases obviously with an increase in tensile strain; meanwhile, the isotropy and value of effective mass or carrier mobility in monolayer h-AlN can also be modulated effectively; the hole mobilities in the armchair direction, especially, will be enhanced dramatically. With a tunable bandgap, high carrier mobilities, and modifiable isotropy, our results indicate that few-layer h-AlN has potential applications in future mechano-electronic devices.

Bonding, structure, and mechanical stability of 2D materials: the predictive power of the periodic table

“…166 Similarly to the onset of interband absorption, the band gaps vary from 2.9 eV for monolayers to B3.5 eV for few-layer assemblies, with a transition from an indirect gap to a direct gap of the bulk. 166,167 Layered h-AlN bulk assemblies do not exist in nature and single layers of h-AlN are difficult to isolate owing to the strong interlayer interaction. Since the absorption intensity increases with the number of layers, few-layer assemblies are of great interest.…”

Few‐layered MoS2 Based Vertical van der Waals p‐n Homojunction by Highly‐efficient N2 Plasma Implantation

“…The observation of electrical characteristics for p-type FET indicates the formation of p-MoS 2 with the Fermi level located closer to the valance band maximum. The mobility of the devices is extracted from the I DS -V GS characteristics by using the relation: [37] ( / )…”

Morphology and carrier mobility of high-B-content BxAl1−xN ternary alloys from an ab initio global search

“…Our results were reliable enough when compared with experimental and other theoretical results. 29–33 We calculated the band structures of these searched ground structures of B x Al 1− x N, as are shown in Fig. 3, and the band structures of wurtzite AlN (w-AlN), hexagonal AlN (h-AlN), wurtzite BN (w-BN), and hexagonal BN (h-BN) are shown in Fig.…”

“…The bandgap of BN is identified to be indirect, 29 but other III-nitrides are direct bandgap semiconductors. 30–34 Therefore, B may change the optical properties of the alloys; 35–37 however, few reports focus on this. Moreover, the morphological uncertainty induced by B also brings difficulties in investigating the properties of the alloys.…”