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Controllable Growth of Vertical Heterostructure GaTexSe1–x/Si by Molecular Beam Epitaxy

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journal contribution
posted on 25.08.2015, 00:00 by Shanshan Liu, Xiang Yuan, Peng Wang, Zhi-Gang Chen, Lei Tang, Enze Zhang, Cheng Zhang, Yanwen Liu, Weiyi Wang, Cong Liu, Chen Chen, Jin Zou, Weida Hu, Faxian Xiu
Two dimensional (2D) alloys, especially transition metal dichalcogenides, have attracted intense attention owing to their band-gap tunability and potential optoelectrical applications. Here, we report the controllable synthesis of wafer-scale, few-layer GaTexSe1–x alloys (0 ≤ x ≤ 1) by molecular beam epitaxy (MBE). We achieve a layer-by-layer growth mode with uniform distribution of Ga, Te, and Se elements across 2 in. wafers. Raman spectroscopy was carried out to explore the composition-dependent vibration frequency of phonons, which matches well with the modified random-element-isodisplacement model. Highly efficient photodiode arrays were also built by depositing few-layer GaTe0.64Se0.36 on n-type Si substrates. These pn junctions have steady rectification characteristics with a rectifying ratio exceeding 300 and a high external quantum efficiency around 50%. We further measured more devices on MBE-grown GaTexSe1–x/Si heterostructures across the full range to explore the composition-dependent external quantum efficiency. Our study opens a new avenue for the controllable growth of 2D alloys with wafer-scale homogeneity, which is a prominent challenge in 2D material research.