The present disclosure relates to a method (100) for depositing a layer on a III-V semiconductor substrate, in which this method comprises providing (102) a passivated III-V semiconductor substrate comprising a III-V semiconductor surface which has a surface passivation layer provided thereon for preventing oxidation of said III-V semiconductor surface. The surface passivation layer comprises a self-assembled monolayer material obtainable by the reaction on the surface of an organic compound of formula R-A, wherein A is selected from SH, SeH, TeH and SiX3. X is selected from H, Cl, O—CH3, O—C2H5, and O—C3H2, and R is a hydrocarbyl, fluorocarbyl or hydrofluorocarbyl comprising from 5 to 20 carbon atoms. The method further comprises thermally annealing (107) the III-V semiconductor substrate in a non-oxidizing environment such as to decompose the self-assembled monolayer material, and depositing (108) a layer on the III-V semiconductor surface in the non-oxidizing environment.