Dispersion of absorption and refractive index of PbTe and Pb1-xEuxTe (x<0.05) below and above the fundamental gap.

摘要: We report extensive experimental and theoretical studies of the frequency dependence absorption constant \ensuremath{\alpha}(\ensuremath{\omega}) index refraction n(\ensuremath{\omega}) in PbTe its pseudobinary alloy ${\mathrm{Pb}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Eu}}_{\mathit{x}}$Te. Mid-infrared transmission experiments on epitaxial layers ${\mathrm{Pb}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Eu}}_{\mathit{x}}$Te (0\ensuremath{\le}x\ensuremath{\le}0.0475, thickness \ensuremath{\approxeq}5 \ensuremath{\mu}m) ${\mathrm{BaF}}_{2}$ substrate were performed range 1000\char21{}5000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ at temperatures from 5 to 300 K. The absolute values as a function can be evaluated yield information both n(\ensuremath{\omega}), due presence interference fringes below fundamental energy gap drop above gap. For model calculation is preferred based nonparabolic Dimmock for energy-momentum relationship \ensuremath{\epsilon}(k) electrons holes. oscillator strength, interband matrix elements ${\mathit{P}}_{\mathrm{\ensuremath{\parallel}}}$ ${\mathit{P}}_{\mathrm{\ensuremath{\perp}}}$ are used that agreement with obtained magneto-optical studies. In procedure fit spectra four parameters used: gap, damping parameter, background refraction. With these functional calculated, derived using Kramers-Kronig transformation. results show nonparabolicity quite important reproduce \ensuremath{\alpha}(\ensuremath{\omega}), via transformation it also substantially influences n(\ensuremath{\omega}). Through causality relation, even frequencies corresponding influenced by shape increasing Eu content increases extremum close ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{g}}$ shifts higher energies. enhancement over index, which determined transitions, becomes weaker.