Stacking effect on the electronic structures of hexagonal GaTe

Abstract

Employing first-principles density functional theory calculations with HSE06 hybrid functional, we investigate stacking-driven modifications on geometric and energy band structures of hexagonal GaTe (h-GaTe) with thickness ranging from bilayer to bulk. Our results show the most energetically favorable stacking order is AB′ type, regardless of the number of layers. The energy band structure of bulk h-GaTe exhibits indirect, quasi-direct and direct band gap for AA′, AB and AB′ stacking, respectively. In particular, as the thickness increases from single- to eleven-layers, both the conduction band minimum and valence band maximum are shifted to the point for AB′ stacking, leading to an indirect-to-direct band gap transition. Further analysis suggests the origin of the band gap transition can be attributed to the enhancement of interlayer coupling introduced by the stacking order.