GaS/ZnS heterojunctions via sulfurization: thin film deposition and characterizations

Thin films of Ga(II)S as produced by sulfurization of gallium oxides are investigated concerning their structures, electrical and optical properties. The weak interlayer coupling of layer compounds facilitates ease of growth into 2D materials or heterojunction structures with other 3D counterparts. In this work, we focused on the superlattices of GaS/ZnS through substitution of oxygen with sulfur atoms starting from their pristine form of GaO/ZnO superlattices mostly put on sapphire substrates, though other substrates have also been used. The chemical substitution was conducted by vaporizing sulfur powders at a proper temperature to achieve a suitable vapor pressure by which the reaction could reach completion. The samples thus obtained were characterized by various techniques of X-ray diffraction (XRD) and grazing angle reflectivity (XRR) measurements from which the crystal structure, interface smoothness and mass density of the constituent layers can be determined. Variable-temperature magneto-transport behaviors and luminescence properties will be discussed in relation to the material processing conditions of the sulfide-based quantum-well structures.