Raman scattering by intervalley carrier-density fluctuations inn-type Ge: Uniaxial stress and resonance effects

We report the observation of light scattering by intervalley density fluctuations in n-type germanium. This scattering appears as a Lorentzian tail near the exciting laser frequency extending up to {~}500 cm^-1. Application of a uniaxial stress of 15 kbar along [111] results in the disappearance of this scattering, thus confirming the assignment to intervalley fluctuations. The effect has been shown to resonate near the E₁ interband gap of Ge ({~}2.1 eV). An analysis of the dependence of the scattering on photon wavelength suggests that the effect is due mainly to intravalley diffusion and not to intervalley scattering.