title: In(x)Ga(₁-x)As nanowires on silicon: one-dimensional heterogeneous epitaxy, bandgap engineering, and photovoltaics.
abstract: We report on the one-dimensional (1D) heteroepitaxial growth of In(x)Ga(1-x)As (x = 0.2-1) nanowires (NWs) on silicon (Si) substrates over almost the entire composition range using metalorganic chemical vapor deposition (MOCVD) without catalysts or masks. The epitaxial growth takes place spontaneously producing uniform, nontapered, high aspect ratio NW arrays with a density exceeding 1 × 10(8)/cm(2). NW diameter (∼30-250 nm) is inversely proportional to the lattice mismatch between In(x)Ga(1-x)As and Si (∼4-11%), and can be further tuned by MOCVD growth condition. Remarkably, no dislocations have been found in all composition In(x)Ga(1-x)As NWs, even though massive stacking faults and twin planes are present. Indium rich NWs show more zinc-blende and Ga-rich NWs exhibit dominantly wurtzite polytype, as confirmed by scanning transmission electron microscopy (STEM) and photoluminescence spectra. Solar cells fabricated using an n-type In(0.3)Ga(0.7)As NW array on a p-type Si(111) substrate with a ∼ 2.2% area coverage, operates at an open circuit voltage, V(oc), and a short circuit current density, J(sc), of 0.37 V and 12.9 mA/cm(2), respectively. This work represents the first systematic report on direct 1D heteroepitaxy of ternary In(x)Ga(1-x)As NWs on silicon substrate in a wide composition/bandgap range that can be used for wafer-scale monolithic heterogeneous integration for high performance photovoltaics.
authors.affiliation: Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801, United States.
authors.forename: Jae Cheol
authors.initials: JC
authors.lastname: Shin
authors.forename: Kyou Hyun
authors.initials: KH
authors.lastname: Kim
authors.forename: Ki Jun
authors.initials: KJ
authors.lastname: Yu
authors.forename: Hefei
authors.initials: H
authors.lastname: Hu
authors.forename: Leijun
authors.initials: L
authors.lastname: Yin
authors.forename: Cun-Zheng
authors.initials: CZ
authors.lastname: Ning
authors.forename: John A
authors.initials: JA
authors.lastname: Rogers
authors.forename: Jian-Min
authors.initials: JM
authors.lastname: Zuo
authors.forename: Xiuling
authors.initials: X
authors.lastname: Li
mesh_terms: D001152:Arsenicals / Q000737:chemistry*; D004574:Electromagnetic Fields; D005708:Gallium / Q000737:chemistry*; D007204:Indium / Q000737:chemistry*; D008027:Light; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry* / Q000528:radiation effects; D010316:Particle Size; D012825:Silicon
chemical_list: D001152:Arsenicals; D007204:Indium; C043055:gallium arsenide; D005708:Gallium; C076773:indium arsenide; D012825:Silicon