Vapor-liquid-solid Growth of III-Nitride Nanowires and Heterostructures by Metal-Organic Chemical Vapor Deposition
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Vapor-liquid-solid Growth of III-Nitride Nanowires and Heterostructures by Metal-Organic Chemical Vapor Deposition J. Su1, M. Gherasimova1, G. Cui1, J. Han1, S. Lim1, D. Ciuparu1, L. Pfefferle1, Y. He2, A. V. Nurmikko2, C. Broadbridge3, A. Lehman4, T. Onuma5, M. Kurimoto5,6, S. F. Chichibu5,6 1 Faculty of Engineering and Applied Science, Yale University, New Haven, CT 06520 2 Division of Engineering, Brown University, Providence, RI 02192 3 Physics Department, Southern Connecticut State University, New Haven, CT 06515 4 Facility for Electron Microscopy, Trinity College, Hartford, CT 06106 5 Institute of Applied Physics, Graduate School of Pure and Applied Sciences, and 21-COE, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Japan 6 NICP, ERATO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi 3320012, Japan ABSTRACT We report flexible synthesis of III-Nitride nanowires and heterostructures by metalorganic chemical vapor deposition (MOCVD) via a catalytic vapor-liquid-solid (VLS) growth mechanism. Indium is used as an in-situ catalyst to facilitate and sustain the stability of liquid phase droplet for VLS growth based on thermodynamic consideration. The employment of mesoporous molecular sieves (MCM-41) helps to prevent the coalescence of catalyst droplets and to promote nucleation statistics. Cathodoluminescence (CL) of GaN nanowires shows near band-edge emission at 370nm, and strong E2 phonon peak is observed at room temperature in Raman scattering spectra. Both binary GaN and AlN nanowires have been synthesized by MOCVD. Three-dimensional AlN/GaN trunk-branch nanostructures are reported to illustrate the versatility of incorporating the VLS mechanism into MOCVD process. INTRODUCTION One-dimensional III-Nitride nanowires and heterostructures offer unique features as nanoscale building blocks for nanoelectronics, photonics, and hybrid biological/chemical systems. The majority of nanowires have been synthesized based on catalytic reaction through vapor-liquid-solid (VLS) growth mechanism.1 The synthesis of III-Nitride nanowires is performed primarily by a near-equilibrium, tube furnace technique which does not offer optimum control or flexibility.2 There is nevertheless a need to enrich the functionality and complexity of the individual building blocks in-situ by using modern heteroepitaxial practices such as molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD).3 Recently we reported our observations in preparing III-Nitride nanowires using a conventional cold wall MOCVD system.4 Here we report on structural and optical characterization of AlN and GaN nanowires and three-dimensional (3D) AlN/GaN heterostructures synthesized by MOCVD.
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EXPERIMENTAL DETAILS Synthesis of the nanowires was carried out in a commercial horizontal MOCVD reactor (Aixtron 200/4 HT-S) using trimethylgallium (TMGa), trimethylaluminum (TMAl), trimethylindium (TMIn), and ammonia (NH3) as sources. Both nitrogen and hydrogen were used as the carrier gas. Unless otherwise specified,
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