Temperature dependence of the vibrations of the Si-H complex in GaAs and AlAs.

Abstract

The temperature dependences between T=5.5 and 300 K of the vibrational absorption of hydrogen-plasma-exposed Si-doped AlAs and GaAs epilayers are presented. The vibrational absorption of the AlAs:Si-H and GaAs:Si-H layers was investigated using high-resolution Fourier-transform spectroscopy. While the bend mode vibration of the Si-H complex was found to have a similar energy in both materials, the stretch mode vibration occurred at a lower energy for the ${\mathrm{Si}}_{\mathrm{Al}}$-H complex. The temperature dependence of the bend and stretch mode line shifts and linewidths are found to be described by a model based on phonon emission and the dephasing relaxation of the vibrations. The broadening of the stretch mode absorption is very rapid and follows a temperature dependence of the form \ensuremath{\sim}${\mathit{e}}_{\mathit{a}}^{\mathrm{\ensuremath{-}}\mathit{E}}$/kT. The small activation energy ${\mathit{E}}_{\mathit{a}}$ of \ensuremath{\sim}9 meV suggests that the linewidth broadening is due to elastic scattering by localized low-energy acoustic phonons.