# Electronic, transport and optical properties of monolayer $\alpha$ and $\beta-$GeSe: A first-principles study

## TL;DR

This study uses first-principles calculations to explore the electronic, transport, and optical properties of monolayer $ ext{GeSe}$ in $ ext{alpha}$ and $ ext{beta}$ forms, revealing their potential for optoelectronic applications.

## Contribution

It provides the first detailed theoretical analysis of $ ext{alpha}$ and $ ext{beta}$-GeSe monolayers, including their electronic band structures, high mobility, and optical anisotropy.

## Key findings

- $ ext{alpha}$-GeSe is a direct band gap semiconductor with 1.6 eV.
- $ ext{beta}$-GeSe is an indirect band gap semiconductor with 2.47 eV.
- $ ext{beta}$-GeSe exhibits high electron mobility of 7.84×10^4 cm^2/V·s along zigzag direction.

## Abstract

The extraordinary properties and the novel applications of black phosphorene induce the research interest on the monolayer group-IV monochalcogenides. Here using the first-principles calculations, we systematically investigate the electronic, transport and optical properties of monolayer $\alpha-$ and $\beta-$GeSe, the latter of which was recently experimentally realized. We found that, monolayer $\alpha-$GeSe is a semiconductor with direct band gap of 1.6 eV, and $\beta-$GeSe displays indirect semiconductor with the gap of 2.47 eV, respectively. For monolayer $\beta-$GeSe, the electronic/hole transport is anisotropic with an extremely high electron mobility of 7.84 $\times10^4$$cm^2/V\cdot {s}$ along the zigzag direction, comparable to that of black phosphorene. Furthermore, for $\beta-$GeSe, robust band gaps nearly disregarding the applied tensile strain along the zigzag direction is observed. Both monolayer $\alpha-$ and $\beta-$GeSe exhibit anisotropic optical absorption in the visible spectrum.