VLS Growth of Position-controlled InP Nanowires and Formation of Radial Heterostructures on Mask-patterned InP Substrate
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VLS Growth of Position-controlled InP Nanowires and Formation of Radial Heterostructures on Mask-patterned InP Substrates Kenichi Kawaguchi1, Hisao Sudo1, Manabu Matsuda1, Mitsuru Ekawa1, Tsuyoshi Yamamoto1, and Yasuhiko Arakawa2 1 Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi, 243-0197 Japan. 2 INQIE and IIS, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan. ABSTRACT Position-controlled InP nanowires (NWs) with separations of 10-100 ȝm were grown by the vapor-liquid-solid (VLS) method using Au-deposited SiO2-mask-patterned InP substrates. Excess indium species diffused from the large mask region formed plural tilted NW-like structures from single openings in addition to the vertical VLS NWs formed by Au catalyst. The introduction of HCl gas during the NW growth was found to efficiently suppress the tilted NWlike structures. Vertical InP NWs without anomalous growth were successfully formed by controlling the HCl flow rate. Moreover, single InP/InAsP/InP quantum wells (QWs) with wurtzite crystal phase structure were epitaxially grown on the sidewall of the position-controlled InP NWs, and two-dimensional arrayed patterns of photoluminescence (PL) coming from the radial QWs were clearly observed in the 1.3-ȝm wavelength region at room temperature. INTRODUCTION III-V compound semiconductor NWs formed by bottom-up growth methods have attracted much attention as building blocks for optoelectronic devices with small sizes because of their distinctive shape [1-5]. In particular, the NWs composed of InP-based materials, which have been well-established for telecom devices, are promising candidates for applications in the near-infrared wavelength region. Introducing heterostructures into the NWs adds functionality to the NWs. Radial heterostructures, where the multi layers are formed on the sidewall of NWs, are expected to have an advantage for creating a larger active region in each NW owing to their high aspect ratio. When we fabricate vertical devices using these NW heterostructures, the NWs are required to be position-defined. VLS growth with the assistance of metal catalytic particles is a promising NW growth technique, and arrayed metal catalytic particles deposited on mask-less substrates have been reported for controlling the position of VLS NWs [5, 6]. In device fabrication, the use of masked substrates is beneficial for electric isolation between sidewall electrodes and substrates. Selective-area NW growth, which is a catalyst-free method, has employed substrates covered with patterned dielectric masks [7, 8]. Some VLS-NW growth studies have been reported on the substrates with mask using chemical beam epitaxy [9, 10] and metalorganic molecular beam epitaxy [11], but the NW growth on these substrates using MOVPE has not been understood well. With regard to the NW pitches, high-density NW growth with small separations in the order of sub-microns have been intensively studied for devices composed of NW bundles, such as solar cells [12]. On the other hand, position-controlled NWs
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