Tailoring the Band Gap in Codoped GaN Nanosheet From First Principle Calculations

Changjiao Ke,Chunling Tian,Yundan Gan

doi:10.3389/fmats.2020.00124

Abstract

To develop an efficient photocatalyst with intense visible light absorption and high charge mobility is important but still remains a problem. In this work, we have explored the electronic properties of C-monodoped, C-Ge and C-Sn codoped GaN nanosheets by the hybrid density functional theory, in order to find the excellent photocatalytic materials. Results indicate the monodoping of C introduces the unoccupied impurity states inside the band gap that serve on recombination centers. Thus the C monodoping is not suitable to ameliorate visible light absorption. Moreover, the C-Ge and C-Sn codoping not only reduce successfully band gap of nanosheet GaN, but also avoid the unoccupied impurity states. The charge-compensated C-Ge and C-Sn codoped GaN nanosheets are energetically favorable for hydrogen evolution but not insufficient to produce oxygen, indicating that they could serve as Z-scheme photocatalysts. In particular, the minimum defect formation energy of C-Ge is negative and lowest. The C-Ge codoped GaN system has dynamic stability. So, the C-Ge codoped nanosheet GaN is one of the most prospective candidates for decompose hydrogen from water.

Highlights

Gallium nitride (GaN) has attracted considerable interest in recent years for its excellent photoelectric properties
The value of the CBM (VBM) is located at the k point while the CBM is at the Ŵ point, which means that the GaN nanosheet is the indirect band gap semiconductor
The electronic properties of C monodoped, C-Ge, and CSn codoped GaN nanosheets have been investigated at the HSE06 level of theory

Summary

Introduction

Gallium nitride (GaN) has attracted considerable interest in recent years for its excellent photoelectric properties. With a large band gap (3.04 eV) (Bastos et al, 2018), GaN is widely used as short-wavelength light-emitting diodes (Ha et al, 2007) and room-temperature laser diodes (Feng et al, 2017). Makes GaN photochemically active only under UV light irradiation. In order to extend the visible light response of GaN, some efforts have been made based on band gap engineering strategies. It was found that Cr-O codoping significantly narrows the band gap of GaN, but this leads to an intermediate band entering the band gap (Pan et al, 2010), which increases the probability of carrier capture. Similar results were obtained for V-O codoped GaN (Meng et al, 2012)

Methods

Results

Conclusion