127. SELF-CATALYZED GAP/GANP CORE/SHELL NANOWIRES ON SI(111) BY GSMBE

Department: Electrical & Computer Engineering
Faculty Advisor(s): Charles Tu

Primary Student
Name: Supanee Sukrittanon
Email: ssukritt@ucsd.edu
Phone: 858-534-3014
Grad Year: 2015

Abstract
Self-catalyzed GaP/GaNP core/shell nanowires on Si(111) by GSMBE S. Sukrittanon1 ,Y. J. Kuang 2, and C. W. Tu1,3 1) Graduate Program of Material Science and Engineering, University of California, San Diego, La Jolla, California 92093, USA 2) Department of Physics, University of California, San Diego, La Jolla, California 92093, USA 3) Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093, USA Dilute nitride GaNP is an interesting material for photovoltaic application due to their tunable bandgaps. Our previous study shows that up to 16% of N could be incorporated into GaP [1]. This means the bandgap of GaNP can be tailored from 1.22 eV to 2.15 eV, cover a wide range of solar spectrum. Moreover, the GaP/GaNP junction has type-II bandgap alignment where photoexcited electron-hole pairs can be automatically separated across the junction without any doping modulation [2]. We have studied self-catalyzed GaP/GaNP core/shell nanowires (NWs) grown on Si (111) by gas-source molecular beam epitaxy (GSMBE). Growth temperature and III/V incorporation ratio were 580 oC and 1.5, respectively for the growth of GaP core NWs. Later, growth temperature was decreased to 520 oC and V/III incorporation ratio was increased to 2.5 for the growth of GaNP shell. Using scanning electron microscopy, vertical and uniform GaP/GaNP core/shell NWs are observed with the density ranges from &#8764;1&#8201;&#8201;107 to &#8764;5&#8201;&#8201;108&#8201;cm&#8722;2 across the Si substrate. GaP/GaNP NWs are hexagonal in shape, following the Si <111> crystal orientation. Average diameters are &#8764;110&#8201;nm for GaP core NWs and &#8764;220&#8201;nm for GaP/GaNP core/shell NWs. Room temperature photoluminescence (PL) signal shows that N is incorporated in the shell with the content of &#8764;0.9%. The PL low-energy tail was significantly reduced, compared to bulk GaNP. Reference [1] W. G. Bi and C. W. Tu, Appl. Phys. Lett. 69, 3710 (1996) [2] S. Kim, B. Fisher, H.-J. Eisler, and M. Bawendi, J. Am. Chem. Soc. 125, 11466 (2003).

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