Detection of Subsurface, Nanometer‐Scale Crystallographic Defects by Nonlinear Light Scattering and Localization

• Published in: Advanced optical materials 2021-08, Vol.9 (16), p.n/a
• Main Authors: Shafiei, Farbod, Orzali, Tommaso, Vert, Alexey, Miri, Mohammad‐Ali, Hung, Pui Yee, Wong, Man Hoi, Alù, Andrea, Bersuker, Gennadi, Downer, Michael C.
• Format: Article
• Language: English
• Subjects: Crystal defects; Crystallography; Current carriers; Diagnosis; Dislocation density; Harmonics; light localization; Light scattering; Localization; Materials science; Microscopes; Optical properties; Optics; Photodegradation; Scanning probe microscopes; scanning probe microscopy; Silicon substrates; subsurface light scattering; subwavelength optics; Threading dislocations
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202002252

Heteroepitaxial crystalline films underlie many electronic and optical technologies but are prone to forming defects at their heterointerfaces. Atomic‐scale defects such as threading dislocations that propagate into a film impede the flow of charge carriers and light degrading electrical/optical performance of devices. Diagnosis of subsurface defects traditionally requires time‐consuming invasive techniques such as cross‐sectional transmission electron microscopy. Using III–V films grown on Si, noninvasive, bench‐top diagnosis of subsurface defects have been demonstrated by optical second‐harmonic scanning probe microscope. A high‐contrast pattern is observed of subwavelength “hot spots” caused by scattering and localization of fundamental light by defect scattering sites. Size of these observed hotspots are strongly correlated to the density of dislocation defects. The results not only demonstrate a global and versatile method for diagnosing subsurface scattering sites but uniquely elucidate optical properties of disordered media. An extension to third harmonics would enable irregularities detection in non‐χ(2) materials making the technique universally applicable. Subsurface atomic‐scale crystallographic threading dislocation defects are detected by noninvasive and fast optical second harmonics scanning probe microscope technique. Light scattering and localization from the electron embedded scattering defect sites create hotspots that are distinguished in the second harmonics regime. The size of these nanometer‐scale hotspots is strongly correlated to the dislocation defects density of the sample.