Direct band gap in gallium sulfide nanostructures

TL;DR

This study uses density functional theory to explore how applying biaxial or uniaxial strain can convert the band gap of monolayer gallium sulfide from indirect to direct, enhancing its potential for optoelectronic applications.

Contribution

It demonstrates that uniaxial strain induces an indirect-to-direct band gap transition in GaS monolayer, providing insights into strain engineering of 2D semiconductors.

Findings

Uniaxial strain shifts GaS from indirect to direct band gap at -10% strain.

GaS monolayer has a sizable band gap suitable for optoelectronic devices.

Poisson's ratio of GaS monolayer is approximately 0.23-0.24, indicating isotropic mechanical properties.

Abstract

The monolayer Gallium sulfide (GaS) was demonstrated as a promising two-dimensional semiconductor material with considerable band gaps. The present work investigates the band gap modulation of GaS monolayer under biaxial or uniaxial strain by using Density functional theory calculation. We found that GaS monolayer shows an indirect band gap that limits its optical applications. The results show that GaS monolayer has a sizable band gap. The uniaxial strain shifts band gap from indirect to direct in Gallium monochalcogenides (GaS). This behavior, allowing applications such as electroluminescent devices and laser. The detailed reasons for the band gap modulation are also discussed by analyzing the projected density of states (PDOS). It indicates that due to the role of p$_y$ orbital through uniaxial strain become more significant than others near the Fermi level. The indirect to direct band gap transition happen at $\varepsilon$=-10y$\%$. Moreover, by investigating the strain energy and transverse response of structures under uniaxial strain, we show that the GaS monolayer has the Poisson's ratio of 0.23 and 0.24 in the zigzag (x) and armchair (y) directions, respectively. Thus, we conclude that the isotropic nature of mechanical properties under strain.