Light Scattering and Localization by Dislocation Scattering Sites

Lattice mismatch between epitaxialy grown crystalline thin film over substrate introduce variety of subsurface defects including threading dislocations. Dislocations defects behave as an acceptor traps for electron and thus acting as Coulomb scattering sites. Multi-scattering and localization of the light from these atomic defects scattering sites was collected by a 50 nm aperture fiber based scanning probe microscope. The localized light appears as few to multiple hundreds of nm optical hotspots based on dislocation density of the film. The smaller hotspots correlated to higher defects density as the multi-scattering light is confined in smaller area. The optical collection was done in second harmonic regime to avoid the dominating surface reflection of fundamental light. We used this approach to introduces a noninvasive tabletop technique capable of optically detecting dislocation atomic defects in III-V materials thin films. New diagnosis and supporting simulation would be shown.