Micro‐Raman study of strain fields around dislocations in GaAs

Abstract

The reliability of microelectronics devices strongly depends on defects like dislocations in the semiconductor wafers. Whereas several methods are routinely used to measure the dislocation density and residual stress in wafers, there is a need of methods to characterize the strain and stress fields around single dislocations with high lateral resolution. The strain and stress fields around single edge and screw dislocations in GaAs are considered, and the corresponding Raman shifts of the phonons are calculated. Due to the finite local resolution, mappings show averaged strain values. Requirements for lateral resolution and signal/noise ratios of the Raman measurements to characterize dislocations are discussed.

Dislocation Generation in Experimentally Shocked Olivine Crystals

“…The dependence of FWHH on dislocation density has been confirmed by recent results from synchrotron‐based Raman spectroscopy that reveal local variation in FWHH near the cores of edge dislocations in gallium nitride (Kokubo et al., 2018). Micro‐Raman analyses of dislocations in gallium arsenide reveal a similar phenomenon: the strain field directly adjacent to a dislocation core results in frequency shifts that are manifested as an increase in the value of FWHH (Irmer & Jurisch, 2007). We do not observe the slight shift in positions for the 825 and 856 cm −1 olivine Raman bands that were observed in experimentally shocked olivine at higher pressure (Harriss & Burchell, 2016).…”

“…In situ observations of Raman measurements in olivine revealed that frequencies of the 825 and 856 cm −1 bands in olivine generally increase linearly with hydrostatic confining pressure (Besson et al., 1982; Yasuzuka et al., 2009), but do not preserve this shift when returned to lower ambient pressure conditions (Farrell‐Turner et al., 2005). In contrast, elastic strain has been measured at distances greater than 1 μm from the cores of dislocations (Irmer & Jurisch, 2007). These observations suggest that the coupled compressive and tensile strain around the cores of dislocations are the primary mechanisms that result in increases in the FWHH of shocked olivine that is preserved at ambient conditions.…”

“…The most intense Raman bands in the olivine Raman spectrum and the bands of interest in this work are found at ∼825 and ∼865 cm −1 corresponding to the asymmetric and symmetric stretching modes of SiO 4 4− (Mouri & Enami, 2008). Local stress deviations near dislocations are associated with strain gradients (Peach & Koehler, 1950) that result in changes in molecular vibrational energies, which result in a shift in Raman band frequencies near dislocation cores in Raman spectra (Irmer & Jurisch, 2007; Kokubo et al., 2018). Raman analyses were performed using a WITec α‐300R confocal Raman microscope (XMB3000‐3003).…”

“…The oxidation‐decoration technique (Kohlstedt et al., 1976) may be used to observe the cores of dislocations in iron‐bearing olivine using either transmitted light or scanning electron microscopy. Micro‐Raman spectroscopy has been used to image local strain around edge dislocations in deformed materials (Irmer & Jurisch, 2007; Kokubo et al., 2018). Transmission electron microscopy (TEM) provides the highest resolution images of dislocations and allows for determination of the burgers vector of dislocations (Leroux et al., 1994).…”

Electronic Raman scattering as an ultra-sensitive probe of strain effects in semiconductors

“…The ultra-sensitivity to strain-induced band-structure changes, which are demonstrated for the electronic Raman technique, can make this technique a valuable tool in such applications. It can also be a valuable tool for probing electronic-structure changes induced by single dislocations 29 , strain engineering of ultra-thin semiconductor crystalline layers 30 and unconventional approaches to heteroepitaxy 31 .…”