Photoluminescence of two-dimensional GaTe and GaSe films

O Del Pozo-Zamudio,N D Kay,A I Dmitriev A I Dmitriev,E A Chekhovich,R C Schofield,N N Kolesnikov,G V Lashkarev,O V Kolosov,B J Robinson,A I Tartakovskii,M Sich,M Bayer,I A Akimov,S Schwarz,D N Borisenko

doi:10.1088/2053-1583/2/3/035010

Abstract

Gallium chalcogenides are promising building blocks for novel van der Waals heterostructures. We report on the low-temperature micro-photoluminescence (PL) of GaTe and GaSe films with thicknesses ranging from 200 nm to a single unit cell. In both materials, PL shows a dramatic decrease by 104–105 when film thickness is reduced from 200 to 10 nm. Based on evidence from continuous-wave (cw) and time-resolved PL, we propose a model explaining the PL decrease as a result of non-radiative carrier escape via surface states. Our results emphasize the need for special passivation of two-dimensional films for optoelectronic applications.

Highlights

The discovery and research of the remarkable properties of two-dimensional (2D) sheets of carbon [1], known as graphene, has sparked interest in other layered materials such as metal chalcogenides (MCs) [2, 3]
We will refer to such features in GaTe films as a ‘free exciton’ peak as opposed to the low energy broad PL bands corresponding to excitons bound to impurities/defects and observed in the range of 1.6–1.7 eV for GaTe
As detailed in the supplementary data and observed in figures 2(b) and 3(b), we find that the proposed model provides a reasonable description of our data using four parameters: the ‘critical’ thickness h0, a parameter describing the amount of light absorbed by the film, and products τrel u1 and τrel u2

Summary

Introduction

The discovery and research of the remarkable properties of two-dimensional (2D) sheets of carbon [1], known as graphene, has sparked interest in other layered materials such as metal chalcogenides (MCs) [2, 3]. As the crystal growth and improvement of thin GaSe films continues [14, 19, 20], further exploration of the physical properties of III–VI materials presented in this work is motivated by their potential use as building blocks for novel van der Waals heterostructures, where materials with a range of bandgaps and band offsets will be required [5, 8]. In contrast to molybdenum and tungsten chalcogenides emitting light efficiently only in films with a single unit cell thickness, III–VI materials are bright light emitters in a range of thicknesses [18]. This may relax the stringent fabrication requirements and add flexibility for novel heterostructured devices such as light emitting diodes [8]

Methods

Results

Conclusion