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Raman spectra from GaAlAs layers with Si3N4 stripes obtained with a microprobe are discussed. The spatial resolution of these Raman spectra was smaller than the scale of the microfabricated features. A significant stress-induced shift in the GaAlAs longitudinal optic (LO) phonon frequency has been observed under 3.5 μm wide Si3N4 stripes. Rapid thermal annealing reduced the LO phonon frequency shift, and thus the stress, under the Si3N4 stripe. A corresponding dramatic change in optical waveguide behavior under the stripe was observed.