Strain Imaging of GaAs by Stimulated Raman Scattering Microscopy

Abstract

Gallium arsenide (GaAs) is a key compound semiconductor used in high-speed and optoelectronic devices, where strain and defect characterization are essential for improving device reliability and performance. However, the conventional approach based on spontaneous Raman spectroscopy suffers from inherently low signal intensity, which severely limits measurement speed. Although stimulated Raman scattering (SRS) offers orders-of-magnitude signal enhancement and faster imaging, the excitation wavelengths commonly used in conventional setups (typically below 1  $\mu$m) are strongly absorbed, hindering SRS signal generation. Here, we overcome this limitation by employing telecom-wavelength SRS microscopy. Clear SRS spectra corresponding to the longitudinal optical (LO) phonon mode near 292 cm ${}^{-1}$ were successfully obtained. The technique enables detection of phonon peak shifts with < 0.2 cm ${}^{-1}$ spectral precision and visualization of local phonon frequency variations associated with surface damage. Compared with conventional Raman mapping, the present method achieves more than two orders of magnitude higher measurement throughput. These results establish telecom-wavelength SRS microscopy as a promising and versatile tool for nondestructive characterization of GaAs.