Infrared Reflectivity Spectra of the Mixed Crystal SystemGa1−xInxSb

Abstract

We report measurements of the far-infrared reflectivity spectra for the pseudobinary system ${\mathrm{Ga}}_{1-x}{\mathrm{In}}_x\mathrm{Sb}$. Data were analyzed with a Kramers-Kronig dispersion analysis and a damped Lorentzian oscillator formalism. For $x<\mathrm{}0.30\mathrm{}$, one TO-phonon mode is evident, whereas for $x>\mathrm{}0.30\mathrm{}$, two TO modes are observed. The variations of the TO-phonon frequencies and the mode strengths do not conform to the traditional types of behavior previously used to describe the long-wavelength optical phonons in pseudobinary alloy systems. An alternative classification scheme, based on the occurrence of gap and/or local modes, is proposed. It is sufficiently general to encompass the previously defined classes of behavior, as well as the behavior we report here for the ${\mathrm{Ga}}_{1-x}{\mathrm{In}}_x\mathrm{Sb}$ system.