GaAs Nanowire pn-Junctions Produced by Low-Cost and High-Throughput Aerotaxy

Abstract

Semiconductor nanowires could significantly boost the functionality and performance of future electronics, light-emitting diodes, and solar cells. However, realizing this potential requires growth methods that enable highthroughput and low-cost production of nanowires with controlled doping. Aerotaxy is an aerosol-based method with extremely high growth rate that does not require a growth substrate, allowing mass-production of high-quality nanowires at a low cost. So far, pn-junctions, a crucial element of solar cells and light-emitting diodes, have not been realized by Aerotaxy growth. Here we report a further development of the Aerotaxy method and demonstrate the growth of GaAs nanowire pnjunctions. Our Aerotaxy system uses an aerosol generator for producing the catalytic seed particles, together with a growth reactor with multiple consecutive chambers for growth of material with different dopants. We show that the produced nanowire pn-junctions have excellent diode characteristics with a rectification ratio of >10 5 , an ideality factor around 2, and very promising photoresponse. Using electron beam induced current and hyperspectral cathodoluminescence, we determined the location of the pn-junction and show that the grown nanowires have high doping levels, as well as electrical properties and diffusion lengths comparable to nanowires grown using metal organic vapor phase epitaxy. Our findings demonstrate that high-quality GaAs nanowire pn-junctions can be produced using a low-cost technique suitable for mass-production, paving the way for industrialscale production of nanowire-based solar cells.

Nanowires for High-Efficiency, Low-Cost Solar Photovoltaics

“…There has been extensive study of the fabrication of single NW devices, such as solar cells and detectors [104][105][106]. However, most of them are with axial p-i-n structures because it is comparatively easy to fabricate contacts [107,108]. However, so far, the highest efficiency of single horizontal NW solar cell is 10.2% reported by Holm et al using GaAsP NWs with radial p-i-n There has been extensive study of the fabrication of single NW devices, such as solar cells and detectors [104][105][106].…”

“…However, so far, the highest efficiency of single horizontal NW solar cell is 10.2% reported by Holm et al using GaAsP NWs with radial p-i-n There has been extensive study of the fabrication of single NW devices, such as solar cells and detectors [104][105][106]. However, most of them are with axial p-i-n structures because it is comparatively easy to fabricate contacts [107,108]. However, so far, the highest efficiency of single horizontal NW solar cell is 10.2% reported by Holm et al using GaAsP NWs with radial p-i-n junctions (Figure 5b) [109].…”

Fundamentals of the nanowire solar cell: Optimization of the open circuit voltage

“…In real world applications, silicon solar cells have by far the largest market penetration, while III/V solar cells are only being used for space applications and as multi-junction solar cells for concentrator photovoltaics. Nanostructured solar cells promise a combination of high efficiency and low cost 179 , in particular when novel growth methods such as aerotaxy [180][181][182] would prove to yield high performance. We like to look at a nanowire solar cell as typical a 2µm thick film on a silicon 59,[183][184][185][186][187] or e.g.…”

“…The substrate can subsequently be cleaned and re-used for a second and third growth run 168 . Alternatively, the substrate costs can be fully eliminated by using aerotaxy [180][181][182] . Challenges with aerotaxy are to vertically align the nanowires into an array, to achieve sizable solar light absorption on a large area as well as to provide electrical contacts.…”

The Geode Process I: Hollow Silica Microcapsules as a High Surface Area Substrate for Semiconductor Nanowire Growth

“…The use of a gaseous medium for Aerotaxy permits efficient modulation of reactor composition, thus enabling the fabrication of heterostructures 47 and p-n junctions. 48 However, the unrestricted motion of growing nanowires in a bulk fluid flow renders them susceptible to nanowire-nanowire collisions that can result in irreversible nanowire aggregation. To avoid such deleterious situations, the concentration of nanowires must remain relatively low.…”