Applied Surface Science 299 (2014) 92–96 Contents lists available at ScienceDirect Applied Surface Science journal h om epa ge: www.elsevier.com/locate/apsusc Fabrication of m-axial InGaN nanocolumn arrays on silicon substrates using triethylgallium precursor chemical vapor deposition approach Chia-Ming Liu a , Yian Tai a,∗ , Kuei-Hsien Chen b , Li-Chyong Chen c a Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10617, Taiwan b Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan c Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan a r t i c l e i n f o Article history: Received 28 November 2013 Received in revised form 28 January 2014 Accepted 29 January 2014 Available online 6 February 2014 Keywords: InGaN m-Axial MOCVD Nanocolumn Triethylgallium a b s t r a c t We demonstrated the catalytic growth of m-axial In x Ga 1-x N (0.10 ≤ x ≤ 0.17) nanocolumn arrays with high crystallinity on silicon substrates using metal–organic chemical vapor deposition with trimethylindium (TMIn), triethylgallium (TEGa), and ammonia as precursors. The high quality of InGaN nanocolumns (NCs) were believed to be due to the utilization of TEGa that achieved less carbon impurities and offered more comparable vapor pressure with that of TMIn at low temperature. In addition, these NCs were grown in non-polar m-axis, which the internal electric field of the InGaN that often deteriorates the device performances might be able to be eliminated. Furthermore, the bandgap of this InGaN can be modulated from UV to visible region simply by tuning the ratio of the precursor during the fabrication. Our results suggest an approach to the fabrication of large-area NCs with a tunable bandgap on a sili- con substrate by the standard MOCVD method that offers an immense opportunity for electronic and photonic applications and allows the scale-up from a research laboratory to industrial scale. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The outstanding thermal and chemical stability of nitride-based materials enable them to operate in high-temperature and hos- tile environments, which make them attractive [1,2]. Among these materials, InGaN is of tremendous interest owing to its versatility of bandgap modulation, i.e., it can be tuned continuously from 0.7 to 3.4 eV [3]. InGaN alloys have been explored for a broad range of applications, such as solid-state photonics and photovoltaics owing to their numerous advantages that include direct bandgap and high carrier mobility, drift velocity, radiation resistance, and optical absorption [4,5]. InGaN also appears to be an ideal mate- rial for the application of water splitting [6] because of its stability in various electrolytic solutions. In addition, thermometric figure of InGaN with high indium content is reasonably good for ther- mopower generation [7]. However, a critical challenge in the fabrication of InGaN is that the growth temperature is much lower for InN (500 ◦ C) than for GaN (1000 ◦ C). Thus, it becomes a trade-off such that lowering the growth temperature of InGaN increases the indium content but reduces the overall quality of the material. On the other hand, ∗ Corresponding author at: Department of Chemical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road Sec. 4, Taipei 106, Taiwan. Tel.: +886 2 2737 6620; fax: +886 2 2737 6644. E-mail address: ytai@mail.ntust.edu.tw (Y. Tai). elevating the growth temperature causes cluster formation and surface segregation of indium owing to the fact that the thermal stabilities of the Ga–N and In–N bonds are different [8]. Although much progress toward overcoming these challenges in the synthe- sis of high-quality InGaN films has been made with the utilization of metal–organic chemical vapor deposition (MOCVD) [9,10], molec- ular beam epitaxy (MBE) [11,12], and hydride vapor-phase epitaxy (HVPE) [13], all these techniques suffer from the lack of a native sub- strate with a suitable lattice constant for epitaxial growth [14,15]. Therefore, efforts have been made to compensate for this deficiency by replacing InGaN thin films with nanocolumns (NCs) [16,17]. Benefitting from their small lateral dimensions, NC structures can relieve the strain within the critical diameters via lateral relax- ation. Thus, they enable high-quality direct heteroepitaxial growth with improved light absorption, charge separation, and directional transport. Indeed, InGaN-based NC devices such as light-emitting diodes, laser diodes, and solar cells have been fabricated that demonstrate improved performance than do the conventional thin- film devices [18–20]. However, the synthesis of homogeneously alloyed high crys- talline ternary InGaN NCs has remained a difficult problem [16]. Despite a great deal of effort, only a small number of groups have been able to achieve the fabrication of single-phase InGaN NCs using different techniques such as HVPE [21,22], MBE [23,24], halide chemical vapor deposition (HCVD) [3,25], and MOCVD [26,27]. The monolithic integration of InGaN with silicon would be a promising approach for the fabrication of optoelectronic devices 0169-4332/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsusc.2014.01.191