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Spectral tuning of localized surface phonon-polariton modes in selective area epitaxy GaN nanowire arrays



Bryan T. Spann, J. Ryan Nolen, Matthew D. Brubaker, Thomas G. Folland, Chase T. Ellis, Joseph G. Tischler, Todd E. Harvey, Joshua D. Caldwell, Kristine A. Bertness


Polar semiconductor materials, such as GaN, InP, SiC et al., offer a basis to manufacture innovative long-wavelength photonic devices.1 Such semiconductors can support propagating and localized surface phonon-polariton (SPhP) resonances that provide highly confined electromagnetic fields. Because the physics of SPhPs are mediated by phonons, exemplary resonant quality factors can be achieved, commensurate with high crystal quality.1,2 The phonon frequency regime for these materials suggest that they could be useful for various applications, e.g., nanoscale THz emitters/detectors, or actively modulated IR nanophotonic devices.1,3 Here, we explore aspects of Raman active of SPhP modes in GaN nanowire arrays grown by selectively area molecular beam epitaxy. As demonstrated in Figure 1A, we observe strong Raman peaks (labeled P1 and P2) within the Reststrahlen band of GaN and red-shifted from the LO phonon. These modes do not occur in bulk GaN and occur around 700 cm-1 (~ 14.3 µm), offering a potential platform for IR device applications. Tuning of the apparent resonances are a function of nanowire pitch and diameter; the diameter tuning is illustrated in Fig. 1B. Optical modeling of the structures’ reflectance was also used as a means of verifying the approximate location and spectral tuning of the SPhP resonances, shown in Fig. 1C. Additional measurements were performed using an FTIR microscope to further establish the spectral behavior. As we show in this work, tuning of the SPhP modes is geometry dependent, thus, by using modern nanofabrication techniques one can design SPhP resonances to fit specific application needs.
Conference Dates
June 11-15, 2018
Conference Location
Conference Title
Nanowire Week


GaN nanowires, phonon-polartions, selective epitaxy


Spann, B. , , J. , Brubaker, M. , Folland, T. , Ellis, C. , Tischler, J. , Harvey, T. , Caldwell, J. and Bertness, K. (2018), Spectral tuning of localized surface phonon-polariton modes in selective area epitaxy GaN nanowire arrays, Nanowire Week, Hamilton, -1 (Accessed July 23, 2024)


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Created April 30, 2018, Updated July 7, 2020