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

Yao Cai,Ying Xie,Yan Liu,Hongxing Xu,Yan Zhao,Chengliang Sun,Yang Zou,Sheng Liu,Shishang Guo,Jian Shi,Chao Gao

doi:10.1063/1.5139664

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.

Highlights

Bulk structures of III–V semiconductors possess attractive properties for the development of light-emitting diodes (LEDs), lasers, and high-power electronics.1–4 Aluminum nitride (AlN) is a unique III–V binary material with the unusual combination of high thermal conductivity and strong dielectric behavior, which makes it promising for advanced device applications.5 Intensive studies6–8 following the discovery of graphene have triggered the development of two-dimensional (2D) III–V binary materials including 2D hexagonal boron nitride (h-BN),9 gallium nitride (GaN),10 andAlN11 for future electronics
24-layer AlN films) by density functional theory (DFT) and indicated that the hexagonal phase is a low-energy stable configuration for the ultrathin AlN film. de Almeida et al.14 investigated the stabilities of the perfect and defective h-AlN and found that defects in h-AlN can lead to a breaking of the planar shape and change the band structure
Lateral and vertical heterostructures of h-GaN/h-AlN and their optoelectronic properties were discussed by Onen et al, and it is found that vertical h-GaN/h-AlN is a composite semiconductor with a tunable fundamental bandgap

Summary

Introduction

Bulk structures of III–V semiconductors possess attractive properties for the development of light-emitting diodes (LEDs), lasers, and high-power electronics. Aluminum nitride (AlN) is a unique III–V binary material with the unusual combination of high thermal conductivity and strong dielectric behavior, which makes it promising for advanced device applications. Intensive studies following the discovery of graphene have triggered the development of two-dimensional (2D) III–V binary materials including 2D hexagonal boron nitride (h-BN), gallium nitride (GaN), andAlN11 for future electronics. Bulk structures of III–V semiconductors possess attractive properties for the development of light-emitting diodes (LEDs), lasers, and high-power electronics.. Intensive studies following the discovery of graphene have triggered the development of two-dimensional (2D) III–V binary materials including 2D hexagonal boron nitride (h-BN), gallium nitride (GaN), and. 24-layer AlN films) by density functional theory (DFT) and indicated that the hexagonal phase is a low-energy stable configuration for the ultrathin AlN film. Following the theoretical prediction of 2D scitation.org/journal/apm h-AlN, the experimental evidence of few-layer h-AlN has been reported.. Encouraged by this, further ab initio theoretical works have been devoted to explore the structural and electronic properties of 2D h-AlN more deeply for promoting its application. Bacaksiz et al. predicted that the hexagonal phase of the bulk h-AlN is a stable direct-bandgap semiconductor and monolayer h-AlN is an indirectbandgap semiconductor with a nonmagnetic ground state. Lateral and vertical heterostructures of h-GaN/h-AlN and their optoelectronic properties were discussed by Onen et al, and it is found that vertical h-GaN/h-AlN is a composite semiconductor with a tunable fundamental bandgap.

Methods

Results

Conclusion