Optical properties of pseudomorphic Si/sub 1-x/Ge/sub x/ for Si-based waveguides at the λ=1300-nm and 1550-nm telecommunications wavelength bands

Abstract

The index of refraction for pseudomorphic Si/sub 1-x/Ge/sub x/ layers grown on Si has been measured at wavelengths /spl lambda/=1310 mn and /spl lambda/=1550 nm. The refractive index values were obtained from waveguide mode profile measurements on a series of Si-Si/sub 1-x/Ge/sub x/-Si waveguides with Ge/sub x/ concentrations between x=0.01 and x=0.1. The index of refraction, n, is significantly larger for light polarized parallel to the growth direction than for light polarized in the plane of the epilayer. This birefringence is consistent with the anisotropic index change predicted using photoelastic theory, given the biaxial strain present in the pseudomorphic Si/sub 1-x/Ge/sub x/ layers. At all wavelengths and polarizations, n varies linearly with the Ge concentration. The pseudomorphic Si/sub 1-x/Ge/sub x/ waveguides layer are stable against lattice relaxation during short anneals at 950/spl deg/C, but exhibit partial relaxation after annealing at 1200/spl deg/C.