Strain-engineered direct-indirect band gap transition and its mechanism in two-dimensional phosphorene

Xihong Peng, Qun Wei, and Andrew Copple
Phys. Rev. B 90, 085402 – Published 4 August 2014

Abstract

Recently fabricated two-dimensional phosphorene crystal structures have demonstrated great potential in applications of electronics. In this paper, strain effect on the electronic band structure of phosphorene was studied using first-principles methods including density functional theory (DFT) and hybrid functionals. It was found that phosphorene can withstand a tensile stress and strain up to 10 N/m and 30%, respectively. The band gap of phosphorene experiences a direct-indirect-direct transition when axial strain is applied. A moderate −2% compression in the zigzag direction can trigger this gap transition. With sufficient expansion (+11.3%) or compression (−10.2% strains), the gap can be tuned from indirect to direct again. Five strain zones with distinct electronic band structure were identified, and the critical strains for the zone boundaries were determined. Although the DFT method is known to underestimate band gap of semiconductors, it was proven to correctly predict the strain effect on the electronic properties with validation from a hybrid functional method in this work. The origin of the gap transition was revealed, and a general mechanism was developed to explain energy shifts with strain according to the bond nature of near-band-edge electronic orbitals. Effective masses of carriers in the armchair direction are an order of magnitude smaller than that of the zigzag axis, indicating that the armchair direction is favored for carrier transport. In addition, the effective masses can be dramatically tuned by strain, in which its sharp jump/drop occurs at the zone boundaries of the direct-indirect gap transition.

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  • Received 18 May 2014
  • Revised 16 July 2014

DOI:https://doi.org/10.1103/PhysRevB.90.085402

©2014 American Physical Society

Authors & Affiliations

Xihong Peng1,*, Qun Wei1,2, and Andrew Copple3

  • 1School of Letters and Sciences, Arizona State University, Mesa, Arizona 85212, USA
  • 2School of Physics and Optoelectronic Engineering, Xidian University, Xi’ an, 710071, P.R. China
  • 3Department of Physics, Arizona State University, Tempe, Arizona 85287, USA

  • *xihong.peng@asu.edu

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Issue

Vol. 90, Iss. 8 — 15 August 2014

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