Raman study under resonant conditions of defects near the interface in a GaAs/Si heterostructure

Abstract

A Raman study has been performed, under resonant conditions, on a GaAs bevelled-edge layer grown on a Si substrate to characterize the optical and crystalline properties of the epilayer near the interface. According to the geometrical characteristics of the sample, a theoretical expression for the Raman intensities profile has been established and compared to the experimental data. This fitting procedure enables us to investigate the absorption coefficient of the GaAs layer due to the disorder-induced softening of the E1 edge. A quantitative analysis of the lattice disorder has been carried out on both longitudinal and transverse optical modes by studying the Raman line-shape evolution versus the laser spot position on the bevel edge. From this study, we have followed the recovery of the crystalline quality of the epilayer while going away from the interface, and evaluated the ‘‘Raman thickness’’ of the dislocated layer. Using the spatial correlation model as a relationship between the disorder amount and the outcoming effects on the Raman line peaks, we have estimated the dislocation density at the heterostructure interface.

Lineshape analysis of Raman scattering from LO and SO phonons in III-V nanowires

“…Correlation length may correspond to the actual grain size, average distance between defects, distribution of atoms in nominally disordered semiconducting alloys, and short range clustering in semiconducting alloys. 5,[7][8][9] According to PCM, the Raman line intensity, I͑͒ at the frequency can be written as 5…”

Phonon Confinement Effect in III-V Nanowires

“…This model was proposed to describe the crystalline quality by introducing a parameter known as correlation length, which is defined as the average size of the material homogeneity region. Correlation length may correspond to the actual grain size, average distance between defects, distribution of atoms in nominally disordered semiconducting alloys, and short range clustering in semiconducting alloys [11,23,[36][37]. However, in our case the downshift of the Raman line gives account for the average size of defect-less regions, the smaller giving rise to larger downshifts.…”

“…In nanostructures the Raman spectrum remains sufficiently similar to that of the corresponding bulk material to facilitate the direct identification of the material. Once the Raman spectra are known, structural defects can be characterized through the mode variation [11,23]. Besides, the observation of any theoretically forbidden mode is a very sensitive probe of lattice distortions.…”

“…This model describe the crystalline quality by the introduction of an important parameter known as "correlation length", defined as the average size of the material homogeneity region i.e., the average distance between two defects [11]. Malayah et al [23] study the misfit dislocation density near the interface in a GaAs/Si hetrostructure by using the Raman line-shape analysis. They calculate the broadening and frequency shift of the LO and TO phonons corresponding to the correlation length (the average distance between two defects) by using PCM as shown in Figure 7.…”

Raman and transmission electron microscopy characterization of InN samples grown on GaN/Al2O3 by molecular beam epitaxy

“…Thus L corresponds to the average distance between two defects, such as dislocations or any other kind of imperfections in the crystal and can be used as a quality factor of the material [5][6][7].…”