Exploiting Phonon-Resonant Near-Field Interaction for the Nanoscale Investigation of Extended Defects

The evolution of wide bandgap semiconductor materials has led to dramatic improvements for electronic applications at high powers and temperatures. However, the propensity of extended defects provides significant challenges for implementing these materials in commercial electronic and optical applications. While a range of spectroscopic and microscopic tools have been developed for identifying and characterizing these defects, such techniques typically offer either technique exclusively, and/or may be destructive. Scattering-type scanning near-field optical microscopy (s-SNOM) is a nondestructive method capable of simultaneously collecting topographic and spectroscopic information with frequency-independent nanoscale spatial precision (approximate to 20 nm). Here, how extended defects within 4H-SiC manifest in the infrared phonon response using s-SNOM is investigated and the response with UV-photoluminescence, secondary electron and electron channeling contrast imaging, and transmission electron microscopy is correlated. The s-SNOM technique identifies evidence of step-bunching, recombination-induced stacking faults, and threading screw dislocations, and demonstrates interaction of surface phonon polaritons with extended defects. The results demonstrate that phonon-enhanced infrared nanospectroscopy and spatial mapping via s-SNOM provide a complementary, nondestructive technique offering significant insights into extended defects within emerging semiconductor materials and devices and thus serves as an important diagnostic tool to help advance material growth efforts for electronic, photonic, phononic, and quantum optical applications.