Giant Band Gap Reduction and Insulator–Metal Transition in Two-Dimensional InX (X = Cl, Br, I) Layers

Abstract

Manipulating the electronic structures of semiconductors by an external electric field promises great potential in future electric technology. However, most of the explored low-dimensional systems only show a weak response under external electric field, and the effective factor, which is defined as ΔEg/U (U is the induced electric potential difference and ΔEg is the change of band gap), is very low. Here, we demonstrated that an unexpected giant band gap modulation is realized in indium halides layers, and the effective factor is much higher than the reported results. Through comprehensive first-principles calculations, we found that two-dimensional InX (X = Cl, Br, I) monolayers are semiconductors with band gaps of 2.59, 2.30, and 2.08 eV, respectively. Remarkably, the band gaps of InX (X = Cl, Br, I) monolayers are dramatically reduced by an external electric field, and the band gap reductions under an electric field of 0.5 V/A found for InCl, InBr, and InI monolayers are 1.51, 1.50, and 1.38 eV, respec...