SPECTROSCOPIC ELLIPSOMETRY OF OPTICAL-TRANSITIONS IN THIN STRAINED SI1-XGEX FILMS

The experimental data obtained from spectroscopic ellipsometry (tan-PSI and cos-DELTA) can be differentiated in Order to determine accurately (+/- 20 meV) the position in photon energy of the optical transitions in the band structure of a crystalline material such as Si or Ge. The technique is applied to Si1-xGex (x<20%) alloyed strained films and enables determination of the so-called E'0, E1 and E2 transition displacements versus the x fraction of Ge present in these alloys.