Abstract
Mechanical manipulation of nanowires (NWs) for their integration in electronics is still problematic because of their reduced dimensions, risking to produce mechanical damage to the NW structure and electronic properties during the assembly process. In this regard, contactless NW manipulation based methods using non-uniform electric fields, like dielectrophoresis (DEP) are usually much softer than mechanical methods, offering a less destructive alternative for integrating nanostructures in electronic devices. Here, we report a feasible and reproducible dielectrophoretic method to assemble single GaAs NWs (with radius 35–50 nm, and lengths 3–5 μm) on conductive electrodes layout with assembly yields above 90% per site, and alignment yields of 95%. The electrical characteristics of the dielectrophoretic contact formed between a GaAs NW and conductive electrodes have been measured, observing Schottky barrier like contacts. Our results also show the fast fabrication of diodes with rectifying characteristics due to the formation of a low-resistance contact between the Ga catalytic droplet at the tip of the NW when using Al doped ZnO as electrode. The current-voltage characteristics of a single Ga-terminated GaAs NW measured in dark and under illumination exhibit a strong sensitivity to visible light under forward bias conditions (around two orders of magnitude), mainly produced by a change on the series resistance of the device.
Highlights
Nowadays, there is still a growing research on inorganic nanostructures such as semiconductor nanowires (NWs) fostered by the great progress achieved during the last decades on advanced synthesis techniques, including molecular beam epitaxy (MBE) [1,2,3,4,5], chemical beam epitaxy (CBE) [6, 7] and chemical vapor deposition (CVD) [8,9,10,11]
Resulting NWs present unique properties such as high NW length-to-diameter ratios—namely aspect ratios—above 100, high surface-to-volume ratios, high crystal quality, and nanometric foot-prints, allowing them to show quantum effects [12,13,14], surface optical phonons [15], ultra-high photo-gains [16, 17], as well as, higher signalto-noise ratios [18], higher sensing surface [18, 19], higher integrability [20,21,22,23,24], higher mechanical properties [24] and Nanotechnology 31 (2020) 225604 faster switching speeds than those obtained by their counter parts the thin film and bulk materials used in conventional electronics and optoelectronics
GaAs NWs used in this work were grown on oxidized Si(111) substrates in a CBE system by the self-assisted VLS mechanism thoroughly depicted in figures 2(a)–(d) and previously described [6, 48, 49]
Summary
There is still a growing research on inorganic nanostructures such as semiconductor nanowires (NWs) fostered by the great progress achieved during the last decades on advanced synthesis techniques, including molecular beam epitaxy (MBE) [1,2,3,4,5], chemical beam epitaxy (CBE) [6, 7] and chemical vapor deposition (CVD) [8,9,10,11]. DEP technique has been successfully used to assemble single NWs made of different materials, including ZnO [16], Si [35], InAs [32], GaN [34], as well as carbon nanotubes (CNTs) [33], between conductive electrodes These studies demonstrated great control over the number of trapped NWs and large assembling yields, above 90% per site, which are essential characteristics for the fabrication of electronic devices (e.g. display, electronics and sensors) with a uniform and compact distribution of NWs along the device active area. Li being the depolarization factor, which depends on the relative orientation of the NW respect to the electric field. εp* and εm* are complex dielectric permittivities of the NW and
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