Stability of Nanometer-Thick Layered Gallium Chalcogenides and Improvements via Hydrogen Passivation

Abstract

The gallium monochalcogenides family, comprising gallium sulfide (GaS), gallium selenide (GaSe), and gallium telluride (GaTe), is capturing attention for its applications in energy storage and production, catalysis, photonics, and optoelectronics. This interest originates from their properties, which include an optical bandgap larger than those of most common transition metal dichalcogenides, efficient light absorption, and significant carrier mobility. For any application, stability to air exposure is a fundamental requirement. Here, we perform a comparative study of the stability of layered GaS, GaSe, and GaTe nanometer-thick films down to a few layers with the goal of identifying the most suitable Ga chalcogenide for future integration in photonic and optoelectronic devices. Our study unveils a trend of decreasing air stability from sulfide to selenide and finally to telluride. Furthermore, we demonstrate a hydrogen passivation process to prevent the oxidation of GaSe with a higher feasibility and durability than other state-of-the-art passivation methods proposed in the literature.

Growth Temperature Effects in Nanoscale-Thick GaTe Films on c-Sapphire Substrate by Molecular Beam Epitaxy: Implications for High-Performance Optoelectronic Devices

“…However, beyond a critical temperature, typically around 500 °C in our experiments, the emergence of the m-GaTe phase becomes evident, as depicted in the XRD spectra presented in Figure . Notably, at optimized higher temperatures, GaTe maintains its preferred monoclinic structure, although GaTe exhibits poor environmental stability. , Even then we could not see the additional peak of any oxide or other phases of GaTe such as Ga 2 O 3 or TeO 2 or Ga 2 Te 3 . ,, So, the absence of additional diffraction peaks from impurities serves as strong evidence of the high purity of the samples.…”