Optical thickness mapping of InGaAsP/InP layers

A two-wavelengths transmission method is presented for measuring the thickness of epitaxial layers with a resolution of better than 10 nm. The measuring speed is high which for the first time makes possible an imagelike presentation of thickness inhomogeneities in layers. A calibration scheme is described which allows quantitative thickness measurements. By the example of measuring buried layers inside a heterostructure the versatile use of the method is demonstrated.