Liquid‐Alloy‐Assisted Growth of 2D Ternary Ga₂In₄S₉ toward High‐Performance UV Photodetection

Abstract 2D ternary systems provide another degree of freedom of tuning physical properties through stoichiometry variation. However, the controllable growth of 2D ternary materials remains a huge challenge that hinders their practical applications. Here, for the first time, by using a gallium/indium liquid alloy as the precursor, the synthesis of high‐quality 2D ternary Ga₂In₄S₉ flakes of only a few atomic layers thick (≈2.4 nm for the thinnest samples) through chemical vapor deposition is realized. Their UV‐light‐sensing applications are explored systematically. Photodetectors based on the Ga₂In₄S₉ flakes display outstanding UV detection ability (R _λ = 111.9 A W⁻¹, external quantum efficiency = 3.85 × 10⁴%, and D* = 2.25 × 10¹¹ Jones@360 nm) with a fast response speed (τ_ring ≈ 40 ms and τ_decay ≈ 50 ms). In addition, Ga₂In₄S₉‐based phototransistors exhibit a responsivity of ≈10⁴ A W⁻¹@360 nm above the critical back‐gate bias of ≈0 V. The use of the liquid alloy for synthesizing ultrathin 2D Ga₂In₄S₉ nanostructures may offer great opportunities for designing novel 2D optoelectronic materials to achieve optimal device performance.