Micro-Raman Cross-Section Study of Ordered Porous III-V Semiconductor Layers
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Micro-Raman Cross-Section Study of Ordered Porous III-V Semiconductor Layers Tetyana R. Barlas1, Nicolas L. Dmitruk1, Nataliya V. Kotova1, Denys O. Naumenko1,2, Valentinas Snitka2 1 Institute for Physics of Semiconductors, National Academy of Sciences of Ukraine, 45 Nauki Prospect, 03028 Kyiv, Ukraine , 2 Research Centre for Microsystems and Nanotechnology, Kaunas University of Technology, Studentu 65, LT-51369 Kaunas, Lithuania
ABSTRACT Porous layers have been obtained by electrochemical etching of n-type III-V semiconductor single crystals (GaAs, InP, and GaP) in water or the ethanol solutions of different acids. The InP porous layers have been shown a more ordered and perfect structure than those of GaP and GaAs. Metal inclusions have been incorporated into the porous layers in an electrochemical cell from an aqueous solution of the Au salt. As found, phonon band intensities are significantly increased in the porous region. The homogeneity of the porous layers prepared has been reliably proved by the Raman micro-spectroscopic mapping of their fresh cleavages. The incorporation of gold into pores leads to a stronger Raman signal of the TO and LO modes, especially in the two-phonon absorption region, and also significantly enhances the photoluminescence of porous layers. INTRODUCTION Porous polar III-V semiconductor compounds having a direct band gap and a large refractive index that is promising for photonics and optoelectronics applications, and their large surface-to-volume ratio offers a great potential for sensors. Moreover, such materials can be employed in the photoelectric devices and solar cells. Surface plasmon or surface plasmon polariton excitation in the metal nanoparticles or on a corrugated metal surface leads to localization, concentration, and local enhancement of electromagnetic fields in their vicinity thus causing an enhancement of many photophysical phenomena such as photoluminescence (PL), infrared absorption (SEIRA), Raman scattering (SERS), photocurrent in barrier structures (plasmonic photovoltaics), electromagnetic forces, electroluminescence etc. Here we propose a facile and cheap method for the fabrication of a new class of nanocomposite materials, viz., ordered porous III-V semiconductor layers with metal nanoparticles incorporated into the pores. Optical properties of nanocomposites have been investigated by micro-Raman spectroscopy, a non-destructive technique giving information on the chemical composition and crystallinity of a sample with a microscopic spatial resolution [1]. Operating with visible-light photons this technique has a high sensitivity for the investigation of vibrational properties of semiconductors and particularly of the Brillouin zone center phonons. Thus, quantum confinement effects or intrinsic stresses in a semiconductor lead to significant changes in phonon frequencies and in
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Raman spectra, respectively [2-4], making the technique attractive for studying a wide range of phenomena. EXPERIMENT Porous layers were obtained by electrochemical etching of n-ty
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