Intensity dependent deflection spectroscopy for the characterization of absorption mechanisms in semiconductors.

We report on a simple method for the characterization of optical absorption in semiconductors at photon energies below the bandgap energy. Therefore, we perform spatially resolved and intensity dependent deflection spectroscopy to measure the local optical absorption. To separate the absorption mechanisms, we take advantage of different intensity scaling of these mechanisms and extract the material parameters by fitting intensity dependent absorption to a physical model. This model takes into account relevant optical absorption processes like linear absorption from defect states, two-photon absorption, and the Franz–Keldysh effect. The method is exemplarily carried out for GaAs, Si, and CdTe. The literature values of the two-photon absorption coefficient are reproduced and the strength of the Franz–Keldysh effect in CdTe is determined for the first time as C FK = [ 8.7 , ... , 16.9 ] × 10 13 m − 1 s − 1 / 2 . [ABSTRACT FROM AUTHOR]