DETERMINATION OF OPTICAL-CONSTANTS OF STRAINED SI1-XGEX EPITAXIAL LAYERS IN THE SPECTRAL RANGE 0.75-2.75 EV

Optical characterization of strained Si1-xGex (0<x less than or equal to 0.30) heteroepitaxial layers has been performed using a spectroscop ic phase modulated ellipsometer in the near infrared to the visible ra nge (0.75-2.75 eV). The dielectric function of the Si1-xGex layers in this spectral range was fitted to an empirical formula with five param eters which were determined using a series of samples with known compo sitions. Accurate ellipsometry measurement of thickness and compositio n has been successfully demonstrated using this formula. This study pr ovides a numerical expression for the optical constants of strained Si 1-xGex in the spectral range of interest for most optoelectronic appli cations. (C) 1997 American Institute of Physics.