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

Abstract

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 (≈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.

Hyperbolic shear polaritons in low-symmetry crystals

“…We anticipate that HShPs may have important implications in the manipulation of phase and directional energy transfer, including radiative heat transport 35 , ultra-fast asymmetric thermal dissipation in the near field 35 and gate-tunability for on-chip all-optical circuitry 36 . Beyond advances in nanophotonics, infrared polariton propagation has been demonstrated as a means for quantifying crystal strain 37 , polytypes 38 , variations in free-carrier density, as well as phononic and electronic properties around defects 39 , thereby also promising a new metrology tool for characterizing low-symmetry ultra-wide-bandgap semiconductors. We highlight that our results are applicable to any material with non-orthogonal optically active transitions and may therefore be extended to other optical phenomena, such as excitons in triclinic ReSe 2 (ref.…”

Refractive Index-Based Control of Hyperbolic Phonon-Polariton Propagation

“…7,11,12 Applications of these properties includehyperlensing 5,[13][14][15] , metasurface-based optical components, 16,17 quantum optics 18 and probes of nanoscale defects. 19,20 In 2014 hBN was first reported as a naturally hyperbolic material with exceptionally low optical losses, 12,21,22 because it supports polaritons derived from optic phonons 21,23 rather than scattering from free carriers. Since then, an extensive list of naturally hyperbolic materials have been cataloged; 24,25 one of the most promising is MoO3 1,[26][27][28] given its record polariton lifetimes (up to 20 ps) 26 and in-plane hyperbolicity.…”

Hyperbolic Shear Polaritons in Low-Symmetry Crystals

“…We anticipate that HShPs may have important implications in the manipulation of phase and directional energy transfer, including radiative heat transport 48,49 , ultrafast asymmetric thermal dissipation in the near-field 49 , and gate-tunability for on-chip all-optical circuitry 50,51 . Beyond nanophotonics advances, infrared polariton propagation has been demonstrated as a means for quantifying crystal strain [52][53][54] , polytypes 55,56 , variations in free-carrier density, as well as phononic and electronic properties around defects 54 with nanoscale precision (< 20nm), thereby promising a novel metrology tool in characterizing low-symmetry ultra-wide bandgap semiconductors. We highlight that our results are applicable to any material with non-orthogonal optically active transitions, and therefore may be extended to other optical phenomena, such as excitons in triclinic ReSe2, which have recently been shown to support multiple in-plane selective excitons 57 .…”