Metal organic vapour-phase epitaxy growth of GaN wires on Si (111) for light-emitting diode applications
© Salomon et al.; licensee Springer. 2013
Received: 18 December 2012
Accepted: 28 January 2013
Published: 7 February 2013
GaN wires are grown on a Si (111) substrate by metal organic vapour-phase epitaxy on a thin deposited AlN blanket and through a thin SiN x layer formed spontaneously at the AlN/Si interface. N-doped wires are used as templates for the growth of core-shell InGaN/GaN multiple quantum wells coated by a p-doped shell. Standing single-wire heterostructures are connected using a metallic tip and a Si substrate backside contact, and the electroluminescence at room temperature and forward bias is demonstrated at 420 nm. This result points out the feasibility of lower cost nitride-based wires for light-emitting diode applications.
KeywordsNitrides Nanowires LED MOVPE 81.07.Gf 81.05.Er 85.60.Jb
III-Nitride semiconductor nanowires (NWs) have recently attracted great interest due to their potential applications including light-emitting diodes (LEDs), lasers, photodetectors, gas sensors and solar cells [1–5]. The direct growth of NWs on conductive substrates benefits from a direct electrical backside contact that can considerably simplify the device processing. In this context, silicon wafers present several attractive advantages to be employed as n- or p-type conductive substrates such as scalability (up to 12 in.), good thermal conductivity and low cost. The planar growth of GaN on Si substrates is challenging because of the large lattice and thermal dilatation mismatches that create high dislocation densities and residual strains. The NW geometry is known to improve these two drawbacks by decreasing the dislocation density along the wire length and releasing the strain with the free surface relaxation. The growth of GaN NWs on Si (111) has been mainly developed by catalyst-free molecular beam epitaxy (MBE) using an intermediate interfacial AlN layer to improve the epitaxial relationships [6, 7]. Such nanowires exhibit excellent optical properties and have been successfully integrated in LED devices . Metal organic vapour-phase epitaxy (MOVPE), which is widespread in the industry for planar growths, has been used to address the growth of catalyst-free GaN wires [9–11]. But surprisingly, the MOVPE growth of GaN wires on Si (111) substrate has been reported only recently using deposited Al  and AlN  intermediate layers. The roles of these thin layers on the epitaxial relationships between the substrate and the wires and their impact on the LED electrical injection have not been reported yet.
These two points will be studied in this paper by growing n-doped GaN wires by MOVPE on a thin AlN layer deposited on n-type Si (111) substrates. The epitaxial relationship of the wire with the AlN/Si interface will be confirmed by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Then, we will demonstrate that such wires can be used as a template to build a complete LED heterostructure based on InGaN/GaN quantum wells grown on the side facets. The electrical properties of single bright-violet electroluminescent wires will be studied to demonstrate the interest of the direct injection from the Si substrate.
The growth is performed in a close-coupled showerhead MOVPE reactor. Si (111) substrates are deoxidized before growth in a 10% HF solution for 1 min. The substrate surface is then cleaned and smoothed with a 20-min bake at 1,100°C and 100 mbar under H2. The direct MOVPE deposition of GaN on Si at high temperature using trimethylgallium (TMGa) results in the formation of hollows in the substrate due to strong chemical reactions . Therefore, unlike to the growth on sapphire, the Si substrate has to be protected first by a thin AlN buffer layer deposited at high temperature using trimethylaluminium (TMAl) and NH3 precursors. Under such growth conditions, the polarity of the AlN layer is Al-polar , and its thickness has no significant influence on the later GaN wire growth. According to our previous work , a thin SiN x layer is first deposited on the AlN surface to prevent GaN planar growth. Self-assembled catalyst-free GaN wires are then grown for 500 s using TMGa and NH3 precursors with a low V/III ratio (approximately 20) and silane injection to favour the vertical growth .
Results and discussion
These n-doped GaN wires (in the 1018-cm−3 range estimated from the width of photoluminescence peaks ) can be used as templates for the growth of a complete LED structure combining unintentionally doped InGaN/GaN multiple quantum wells (MQWs) on the side facets and convenient doping junctions. Nominal In0.18Ga0.82N (1 nm)/GaN (10 nm) MQWs are grown using trimethylindium (TMIn), triethylgallium (TEGa) and NH3 as described in  and coated by a p-GaN layer doped in the 1017-cm−3 range using TMGa, NH3 and bis(cyclopentadienyl)magnesium (Cp2Mg).
In summary, we have shown the possibility to grow self-assembled vertically aligned GaN wires on the Si (111) substrate using a thin AlN intermediate layer. The epitaxial relationship of the GaN wires/AlN/Si (111) has been studied by XRD and GIXRD. As shown by HRTEM observations and in agreement with literature, the high growth temperature of AlN leads to the formation of an amorphous (or nanocrystallized) SiN x layer between the Si and the AlN that does not affect the epitaxial relationship. The wires were then used as templates for the growth of a complete LED structure, and the electrical continuity between the Si substrate and the n-GaN wire core allows the injection of electrons in the structure using a backside contact. A violet electroluminescence at 420 nm of single wires has been demonstrated and provides a low cost wire-based LED alternative for optoelectronic devices on Si when the voltage threshold will be reduced.
The authors thank the French BM32 beamline staff of the ESRF synchrotron, V. Favre-Nicolin for the scientific discussion and J. Dussaud for the technical help. This work has been funded in part by the French government ANR Sincrone and Carnot Eclairage projects.
- Dong Y, Tian B, Kempa TJ, Lieber CM: Coaxial group III-nitride nanowire photovoltaics. Nano Lett 2009, 9: 2183–2187. 10.1021/nl900858vView ArticleGoogle Scholar
- Qian F, Gradecak S, Li Y, Wen CY, Lieber CM: Core/multishell nanowire heterostructure as multicolour, high-efficiency light-emitting diodes. Nano Lett 2005, 5: 2287–2291. 10.1021/nl051689eView ArticleGoogle Scholar
- Qian F, Li Y, Gradecak S, Park HG, Dong Y, Ding Y, Wang ZL, Lieber CM: Multi-quantum-well nanowire heterostructures for wavelength-controlled lasers. Nat Mater 2008, 7: 701–706. 10.1038/nmat2253View ArticleGoogle Scholar
- Dobrokhotov V, McIlroy DN, Grant Norton M, Abuzir A, Yeh WJ, Stevenson I, Pouy R, Bochenek J, Cartwright M, Wang L, Dawson J, Beaux M, Berven C: Principles and mechanisms of gas sensing by GaN nanowires functionalized with gold nanoparticles. J Appl Phys 2006, 99: 104302. 10.1063/1.2195420View ArticleGoogle Scholar
- Jacopin G, De Luna Bugallo A, Levenus P, Rigutti L, Julien FH, Zagonel LF, Kociak M, Durand C, Salomon D, Chen XJ, Eymery J, Tchernycheva M: Single-wire light-emitting diodes based on GaN wires containing both polar and nonpolar InGaN/GaN quantum wells. Appl Phys Express 2012, 5: 014101. 10.1143/APEX.5.014101View ArticleGoogle Scholar
- Bertness KA, Roshko A, Sanford NA, Schlager JB, Gray MH: Formation of AlN and GaN nanocolumns on Si(111) using molecular beam epitaxy with ammonia as nitrogen source. Phys Stat Sol (c) 2005, 2: 2369. 10.1002/pssc.200461523View ArticleGoogle Scholar
- Songmuang R, Landré O, Daudin B: From nucleation to growth of catalyst-free GaN nanowires on thin AlN buffer layer. Appl Phys Lett 2007, 91: 251902. 10.1063/1.2817941View ArticleGoogle Scholar
- Guo W, Zhang M, Banerjee A, Bhattacharya P: Catalyst-free InGaN/GaN nanowire light emitting diodes grown on (001) silicon by molecular beam epitaxy. Nano Lett 2010, 10: 3355. 10.1021/nl101027xView ArticleGoogle Scholar
- Bergbauer W, Strassburg M, Kölper C, Linder N, Roder C, Lähnemann J, Trampert A, Fündling S, Li SF, Wehmann HH, Waag A: Continuous-flux MOVPE growth of position-controlled N-face GaN nanorods and embedded InGaN quantum wells. Nanotechnology 2010, 21: 305201. 10.1088/0957-4484/21/30/305201View ArticleGoogle Scholar
- Hersee SD, Sun X, Wang X: The controlled growth of GaN nanowires. Nano Lett 1808, 2006: 6.Google Scholar
- Koester R, Hwang JS, Durand C, Le Si Dang D, Eymery J: Self-assembled growth of catalyst-free GaN wires by metal-organic vapour phase epitaxy. Nanotechnology 2010, 21: 015602. 10.1088/0957-4484/21/1/015602View ArticleGoogle Scholar
- Song KY, Navamathavan R, Park JH, Ra YB, Ra YH, Kim JS, Lee CR: Selective area growth of GaN nanowires using metalorganic chemical vapor deposition on nano-patterned Si(111) formed by the etching of nano-sized Au droplets. Thin Solid Films 2011, 520: 126. 10.1016/j.tsf.2011.06.083View ArticleGoogle Scholar
- Bavencove AL, Salomon D, Lafossas M, Martin B, Dussaigne A, Levy F, André B, Ferret P, Durand C, Eymery J, Le Si Dang D, Gilet P: Light emitting diodes based on GaN core/shell wires grown by MOVPE on n-type Si substrate. Electron Lett 2011, 47: 765. 10.1049/el.2011.1242View ArticleGoogle Scholar
- Dadgar A, Poschenrieder M, Bläsing J, Contreras O, Bertram F, Riemann T, Reiher A, Kunze M, Daumiller I, Krtschil A, Diez A, Kaluza A, Modlich A, Kamp M, Christen J, Ponce FA, Kohn E, Krost A: MOVPE growth of GaN on Si(111) substrates. J Cryst Growth 2003, 248: 556.View ArticleGoogle Scholar
- Radtke G, Couillard M, Botton GA, Zhu D, Humphreys CJ: Structure and chemistry of the Si(111)/AlN interface. Appl Phys Lett 2012, 100: 011910. 10.1063/1.3674984View ArticleGoogle Scholar
- Haffouz S, Beaumont B, Gibart P: Effect of magnesium and silicon on the lateral overgrowth of GaN patterned substrates by metal organic vapor phase epitaxy. J Nitride Semicond Res 1998, 3: 8.Google Scholar
- Meng WJ, Heremans J, Cheng YT: Epitaxial growth of aluminium nitride on Si(111) by reactive sputtering. Appl Phys Lett 2097, 1991: 59.Google Scholar
- Koester R, Hwang JS, Salomon D, Chen XJ, Bougerol C, Barnes JP, Le Si Dang D, Rigutti L, Tchernycheva M, Durand C, Eymery J: M-plane core-shell InGaN/GaN multiple quantum wells on GaN wires for electroluminescent devices. Nano Lett 2011, 11: 4839.4.View ArticleGoogle Scholar
- Ishikawa H, Zhang B, Egawa T, Jimbo T: Valence-band discontinuity at the AlN/Si interface. Jpn J Appl Phys 2003, 42: 6413. 10.1143/JJAP.42.6413View ArticleGoogle Scholar
- Baur J, Maier K, Kunzer M, Kaufmann U, Schneider J: Determination of the GaN/AlN band offset via the (−/0) acceptor level of iron. Appl Phys Lett 1994, 65: 2211. 10.1063/1.112764View ArticleGoogle Scholar
- Egawa T, Zhang B, Nishikawa N, Ishikawa H, Jimbo T, Umeno M: InGaN multiple-quantum-well green light-emitting diodes on Si grown by metalorganic chemical vapor deposition. J Appl Phys 2002, 91: 528. 10.1063/1.1408264View ArticleGoogle Scholar
- Sekiguchi H, Kishino K, Kikuchi A: Emission color control from blue to red with nanocolumn diameter of InGaN/GaN nanocolumn arrays grown on same substrate. Appl Phys Lett 2010, 96: 231104. 10.1063/1.3443734View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.