Effects of interband excitations on Raman phonons in heavily dopedn−Si

Abstract

R~vvi~v1-active interwnduction-bandtransitions from the h, to h, 2 bands in heavily doped n-Sj (n 1.$ X 10 cm «) interfere with the zone-center optical phonon to produce Pano-type asymmetric phonon line shapes typical of a discrete-continuum interaction. %e have studied the line shapes as a function of exciting frequency and uniaxial stress along the [001] and [111]directions. The asymmetry is removed under[001] uniaxial stress for the doublet component of the phonon that couples to the stress-depleted doublet valley, and is enhanced for the singlet component that couples to the carriermdmiced singlet valley. &e have catculated from microscopic theory the parameters that describe the Pano interaction -the asymmetry parameter, the broadening, and the frequency shift due to the self-energy of the phonon deformationpotential interaction with the free electrons in the conduction-band valley. These paameters have been calculated for zero stress and a high stress along the [001] direction, and are found to be in excellent agreement with experiment. %e have also investigated the second-order acoustical-phonon scattering [2TA(X)]; it shows no change in line shape for heavily doped n-Si. Under uniaxial stress along the [001] and [111] directions, it exhibits only the hydrostatic shift, as does pure Si, which was measured for comparison.

Constraints on micro-Raman strain metrology for highly doped strained Si materials

“…13-the absolute value of the relative Raman Si peak becoming more redshifted as a function of increasing carrier concentration. This theory is subject to adjustment due to an error in the value of the deformation potential of the Si conduction band used by the authors, 16 which may account for some of the difference between the theory and our experimental data. A linear fit of bulk and strained Si data points indicates that the theory developed for bulk Si may also be applied to strained Si.…”

Hydrostatic pressure dependence of the luminescence and Raman frequencies in polyfluorene

“…The asymmetry parameter (1/q) depends on the average electron-phonon matrix element M and the Raman matrix elements between the ground and excited states of the phonon and electron. 37 The broadening parameter is given by that when qϭϪ(Ϫ 0 )/⌫, the spectral function I() will reveal an ''antiresonance'' close to the value of phonon frequency.…”

Micro-Raman measurement of bending stresses in micromachined silicon flexures

“…From (5), (8) and (9), we obtain (10) As before, for arbitrary and propagating along , the Raman spectrum contains a single peak corresponding to the eigenvector . From (8), therefore, the change in the Raman shift is simply (11) For , and using the phonon deformation potentials of Anastassakis et al [16], we obtain (12) and using the phonon deformation potentials of Chandrasekhar et al [15], we obtain (13) In both (12) and (13), is expressed in units of megapascals and in . Corresponding to any measured change in the Raman shift, therefore, is a uniquely determined value of the local uniaxial stress in the flexure.…”

“…On the other hand, the phonon deformation potentials are known only to and two independent measurements report values that differ, on average, by about 20% (see Table II). Chandrasekhar, Renucci, and Cardona [15] measured one set using backscattering experiments, while Anastassakis, Cantarero and Cardona [16] revised these values using transmission spectroscopy. The latter values are expected to be more accurate since they exclude any possible surface relaxation effects.…”