(a) Layout of the pump-and-probe setup. (b) Definition of the polarization geometry with respect to the sample axes.
Grayscale map of the transmittance (dark: low transmittance, light: high transmittance) in sample III at 300 K for the components with (a) and (b) after exposing two slightly overlapping, rectangular areas indicated by the corners. The dashed lines in (a) mark two line scans across the exposed (A) and unexposed (B) areas. (c) Corresponding PL intensity map at 100 K measured by . The change in the PL intensity between the exposed and unexposed area is about a factor of 2.
Transmittance in sample III for along two line scans across the exposed (A) and unexposed areas (B), as indicated in Fig. 2(a).
Transmittance spectra recorded over a macroscopic area of sample III for (solid line) and (dashed line) at room temperature.
Raman spectra of the four -plane GaN films (samples I–IV) and of the -plane GaN film (sample V) at room temperature. Note that the spectra are vertically shifted and rescaled for clarity.
(a) Position of the Raman line scans with respect to the exposed area on sample III. (b) Change in phonon wavenumbers of the -Raman line for the line scans labeled A to E as indicated in (a) recorded at . The curves A to E have been shifted by with respect to each other for clarity.
PR spectra for at different points (1–7) of sample III at . The spectra have been vertically shifted with respect to each other by 3 units for clarity. Inset: estimated relation of the measured points with respect to the two exposed rectangular areas on the sample.
Calculated transition energies (a) and (b) as a function of the in-plane strain and for sample III at . The dot in (a) and (b) marks the in-plane strain of the unexposed sample.
Transition energies (filled squares) and (dots) for different sample positions extracted from the PR spectra at and corresponding in-plane strain values (squares) and (circles) as derived from the calculations. The positions 4 and 5 correspond to the exposed area.
Film thickness , out-of-plane strain , and phonon wavenumber of the -Raman line for the strained -plane GaN films (I–IV) and the unstrained -plane GaN film (V). All measurements were performed at room temperature.
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