The accommodation of lattice mismatching in InPAs layers with thickness from one monolayer to 200 A˚ grown on InP substrates is measured by extended x‐ray‐absorption fine structure. Measured critical thicknesses agree with model calculations. In the layers beyond the critical thickness, gradual lattice accommodation with increase of the layer thickness is observed. The lattice accommodation mechanism beyond the critical thickness is discussed by comparison with the calculations. ©1995 American Institute of Physics.