In situ measurement of the optical absorption coefficient of porous silicon

Detailed experimental procedure of an in situ photoelectrical technique app lied to porous silicon absorption coefficient measurement is described. In this technique, the underlying silicon substrate is used as a photodetector of the monochromatic light intensity transmitted by the porous layer. In p articular, the investigation of spectral range validity of this technique h as evidenced that at high photon energy, the porous silicon photoluminescen ce (PL) is excited and contributes to the photocurrent. It is shown that th is PL contribution can be readily separated from that of the directly trans mitted light, providing two benefits: first, the high accuracy of the measu rement remains unaffected by the PL at high excitation energy, which justif ies the application to photon energy as high as 3 eV, and second, the PL co mponent can be further exploited to measure the porous silicon PL quantum e fficiency. Typical absorption coefficient spectra obtained by this techniqu e are then recalled. They are discussed in the frame of a model based on th e analysis of the absorption coefficient of an ensemble of different quantu m-size silicon crystallites. (C) 2001 American Institute of Physics.