We have studied Raman scattering from 〈100〉 GaAs samples implanted with 270-keV As+ ions with various fluences up to 3.2×1014 cm−2. In addition to phonon density of states effects, we observe a softening and asymmetric broadening of the allowed LO phonon while the small symmetry forbidden TO phonon remains almost unchanged. The behavior of the LO and TO modes can be explained quantitatively on the basis of a ‘‘spatial correlation’’ model related to q-vector relaxation induced by the damage. Our interpretation is quite general and makes it possible to use Raman spectra to evaluate an average size of undamaged regions in semiconductors.

Raman spectroscopy (RS) has been used as a technique for the characterization of well-aligned IrO

We have measured the temperature dependence of the spectral features in the vicinity of direct band-edge excitonic transitions of single crystals from 25 to 300 K using piezoreflectance (PzR). From a detailed lineshape fit of the PzR spectra, the energies and broadening parameters of the A and B excitons have been determined accurately. The origin of these excitonic transitions is discussed. The transition energies and their splittings vary smoothly with the tungsten composition x, indicating that the natures of the direct band edges are similar for the compounds. In addition, the parameters that describe the temperature variation of the energies and broadening function of the excitonic transitions are evaluated and discussed.

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