Two-wavelength transmission: A rapid and precise method for measuring the light absorption in semiconductors

By means of two-wavelength transmission the reflection and scattering losses at surfaces are cancelled out experimentally. A signal which is directly proportional to the light absorption is derived and measured in real time. The performance of the method for measuring the concentrations of EL2 in GaAs, of Fe in InP and of the thicknesses of InGaAsP/InP layers is demonstrated.