Gallium arsenide substrate comprising a surface oxide layer with improved surface homogeneity

A gallium arsenide substrate which exhibits at least one surface having a surface oxide layer comprising gallium and arsenic oxides, the surface oxide layer having a degree of lateral homogeneity characterized by a variation of a laterally resolved background-corrected measurement signal whose distribution percentile of 1% normalized to a substrate average of a plurality of phase shift signals measured across an entirety of the at least one surface is greater than −0.005, as determined by an ellipsometric lateral substrate mapping with an optical surface analyzer, wherein the substrate has a diameter of at least 100 mm and at most 200 mm.