Structural and Dynamical Properties of Short-Period GaN/AlN Superlattices: Experiment and Theory
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XVIII INTERNATIONAL SYMPOSIUM “NANOSTRUCTURES: PHYSICS AND TECHNOLOGY”, MINSK, REPUBLIC OF BELARUS, SEPTEMBER, 2020. NANOSTRUCTURE CHARACTERIZATION
Structural and Dynamical Properties of Short-Period GaN/AlN Superlattices: Experiment and Theory I. A. Eliseyeva,*, V. Yu. Davydova,**, E. M. Roginskiia,***, Yu. E. Kitaeva,****, A. N. Smirnova,*****, M. A. Yagovkinaa,******, D. V. Nechaeva,*******, V. N. Jmerika,********, and M. B. Smirnovb,********* a
b
Ioffe Institute, St. Petersburg, 194021 Russia St.-Petersburg State University, St. Petersburg, 199034 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] ****e-mail: [email protected] *****e-mail: [email protected] ******e-mail: [email protected] *******e-mail: [email protected] ********e-mail: [email protected] *********e-mail: [email protected]
Received June 23, 2020; revised July 23, 2020; accepted July 27, 2020
Abstract—We report the results of systematic experimental and theoretical studies of structural and dynamical properties of short-period GaN/AlN superlattices. The multilayer structures with the thicknesses of the constituent layers varying from two to several monolayers are grown using the submonolayer digital molecular beam epitaxy technique. In the framework of density functional theory, the lattice dynamics properties of the superlattices are studied. Good agreement between the experiment and theory is found, which made it possible to establish unambiguously a relationship between the features observed in the Raman spectra and the microscopic nature of the acoustic and optical phonon modes. The results obtained enhance the capabilities of Raman spectroscopy as a fast and non-destructive characterization method of short-period GaN/AlN superlattices and can be used to optimize growth process parameters for the fabrication of structurally perfect low-dimensional heterostructures. Keywords: GaN/AlN superlattices, molecular beam epitaxy, group theory analysis, density functional theory, lattice dynamics, Raman spectroscopy DOI: 10.1134/S1063782620120052
1. INTRODUCTION The great scientific interest in low-dimensional epitaxial heterostructures based on wide-gap semiconductors GaN, AlN and their alloys is due to their unique ability to create optoelectronic devices operating in a very wide spectral region. In this case, interband and exciton transitions are the basis for the functioning of photonic heterostructures of the middle UV range, while intraband transitions will be used in the detection and generation of radiation in the IR and THz ranges [1, 2]. Such devices are promising for use in medicine, security systems, space technology, etc. Among the most important elements of such devices are short-period GaN/AlN superlattices (SLs), with the thicknesses of the constituent layers varying from
one to several monolayers (ML). Quality control of the grown structures is extremely important for creation of high-quality optoelectronic devices. Raman spectroscopy is one of the most e
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