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AFM Characterization of GaAs/AlGaAs Waveguides
Kazuhiko HOSOMI Masataka SHIRAI Kenji HIRUMA Junji SHIGETA Toshio KATSUYAMA
IEICE TRANSACTIONS on Electronics
Publication Date: 1996/11/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Quantum Effect Devices and Their Fabrication Technologies)
GaAs, waveguide, scattering, surface roughness,
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The direct measurement of sidewall roughness on a ridge-type GaAs waveguide was performed using an atomic force microscope (AFM) combined with a scanning electron microscope (SEM). The ridge sidewall of a GaAs waveguide formed by wet-etching and the ridge sidewall formed after regrowth of a 2.45-µm GaAs/AlGaAs epitaxial layer on the same waveguide were observed using introducing the technique for sample slanting. The observed power spectral density was used to determine the scattering loss caused by the sidewall roughness. It was found that the ridge-type GaAs waveguide for light wave transmission had a scattering loss of 0.029 dB/cm in the as-etched ridge state and a scattering loss of 0.17 dB/cm after regrowing the cover GaAs/AlGaAs epitaxial layer. A leaky GaAs/AlGaAs waveguide for polariton-quantum-wave trans-mission had a scattering loss of 1.3l0-5 dB/cm, which means that the scattering loss is negligible. Furthermore, it was found that a periodical surface fluctuation (spatial frequency 2.2 µm-1) along the waveguide appeared after the regrowth of the epitaxial layer. Thus, this method is useful for direct observation of sidewall roughness and can be used to quantitatively determine the sidewall scattering loss.