Raman analysis of phonon modes in a short period AlN/GaN superlattice. (March 2018)

• Record Type: Journal Article
• Authors: Sarkar, Ketaki; Datta, Debopam; Gosztola, David J.; Shi, Fengyuan; Nicholls, Alan; Stroscio, Michael A.; Dutta, Mitra
• Is Part Of: Superlattices and microstructures. Volume 115(2018)
• Page Start: 116
• Page End: 122
• Publication Date: 2018-03
• Subjects: Superlattice -- Raman spectroscopy -- Interface phonons -- Dielectric continuum model -- Aluminum nitride -- Gallium nitride; Superlattices as materials -- Periodicals; Microstructure -- Periodicals; Semiconductors -- Periodicals; Superréseaux -- Périodiques; Microstructure (Physique) -- Périodiques; Semiconducteurs -- Périodiques; 621.38152
• DOI: 10.1016/j.spmi.2018.01.021
• Languages: English
• ISSNs: 0749-6036

Abstract

Abstract: AlN/GaN-based optoelectronic devices have been the subject of intense research underlying the commercialization of efficient devices. Areas of considerable interest are the study of their lattice dynamics, phonon transport, and electron-phonon interactions specific to the interface of these heterostructures which results in additional optical phonon modes known as interface phonon modes. In this study, the framework of the dielectric continuum model (DCM) has been used to compare and analyze the optical phonon modes obtained from experimental Raman scattering measurements on AlN/GaN short-period superlattices. We have observed the localized E 2 (high), A 1 (LO) and the E 1 (TO) modes in superlattice measurements at frequencies shifted from their bulk values. To the best of our knowledge, the nanostructures used in these studies are among the smallest yielding useful Raman signatures for the interface modes. In addition, we have also identified an additional spread of interface phonon modes in the TO range resulting from the superlattice periodicity. The Raman signature contribution from the underlying Alx Ga1-x N ternary has also been observed and analyzed. A temperature calibration was done based on Stokes/anti-Stokes ratio of A 1 (LO) using Raman spectroscopy in a broad operating temperature range. Good agreement between the experimental results and theoretically calculated calibration plot predicted using Bose-Einstein statistics was obtained. Highlights: Short-period AlN/GaN superlattice have been characterized using Raman spectroscopy under back-scattering geometry. The nanostructures used in these studies are among the smallest yielding useful Raman signatures for the interface modes. Dispersion relation of the superlattice has been obtained theoretically using dielectric continuum model (DCM). Calibration of Raman response at high-temperature by measuring Stokes/Anti-Stokes ratio of phonon mode has been obtained.