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Gallium sulfide, GaS, is a chemical compound of gallium and sulfur. The normal form of gallium sulfide as made from the elements has a hexagonal layer structure containing Ga2 units which have a Ga-Ga distance of 248pm. This layer structure is similar to GaTe, GaSe and InSe. An unusual metastable form, with a distorted wurtzite structure has been reported as being produced using MOCVD. The metal organic precursors were di-tert-butyl gallium dithiocarbamates, for example GaBu2 and this was deposited onto GaAs. The structure of the GaS produced in this way is presumably Ga S.
Single layers of gallium sulfide are dynamically stable two-dimensional semiconductors, in which the valence band has an inverted Mexican-hat shape, leading to a Lifshitz transition as the hole-doping is increased.