Composition ratio dependent refractive index and optical bandgap of nonstoichiometric Si1−xGex on silicon

Nonstoichiometric Si
_1-x
Ge
_x
films fabricated by plasma enhanced chemical vapor deposition (PECVD) with different flounce ratios are demonstrated to show the composition ratio dependent optical properties, including refractive index, bandgap and optical absorption. By increasing the fluence ratio from 0.2 to 0.5, the refractive index of Si
_1-x
Ge
_x
film raises from 3.527 to 3.927, with the absorption coefficient enlarging from <;<;1cm
^-1
to 31.12 cm
^-1
.