Surface Recombination Velocity Measurements of Efficiently Passivated Gold-Catalyzed Silicon Nanowires by a New Optical Method

Demichel, Olivier; Calvo, V.; Besson, Adrien; Noé, Pierre; Salem, B.; Pauc, N.; Oehler, Fabrice; Gentile, P.; Magnéa, N.

doi:10.1021/nl903166t

Cited by 57 publications

(59 citation statements)

References 28 publications

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“…This value is rather small compared with the bulk case and arises from considerably reduced carrier lifetime in the NW owing to the extremely efficient surface recombination on the non-passivated surfaces. This is in agreement with previous works performed on the study of the passivation of Si NWs which showed no photoluminescence signal from electron- hole (e-h) recombination emerging from as grown NW samples [22][23][24] due to the extremely high values of the surface recombination velocities. Instead, a passivation step was necessary to observe efficient e-h recombination, where native oxide was replaced by a thermally grown SiO 2 layer on a chemically cleaned Si surface with final annealing in the forming gas.…”

Section: Resultssupporting

confidence: 93%

Geometrical control of photocurrent in active Si nanowire devices

et al. 2012

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Section: Resultssupporting

confidence: 93%

Geometrical control of photocurrent in active Si nanowire devices

et al. 2012

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“…3, 4 The first effect has recently been quantified by an original optical method for silicon NWs. 5,6 The surface charge traps induce a pinning of the Fermi-level at the surface. A depletion shell appears and the electronic channel available for carriers is narrowed.…”

mentioning

confidence: 99%

“…According to Ref. 6, the mean slope of the gray dashed lines is linked to the surface recombination velocity ͑SRV͒ of the NWs. One should note that in the case of uncapped NWs, we measure SRV while the capped the recombination velocity corresponds to the GaAS/AlGaAs interface.…”

mentioning

confidence: 99%

Impact of surfaces on the optical properties of GaAs nanowires

Demichel

Heiß

Bleuse

et al. 2010

Applied Physics Letters

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The effect of surfaces on the optical properties of GaAs nanowires is evidenced by comparing nanowires with or without an AlGaAs capping shell as a function of the diameter. We find that the optical properties of unpassivated nanowires are governed by Fermi-level pinning, whereas, the optical properties of passivated nanowires are mainly governed by surface recombinations. Finally, we measure a surface recombination velocity of 3 ϫ 10 3 cm s −1 one order of magnitude lower than values previously reported for ͕110͖ GaAs surfaces. These results will serve as guidance for the application of nanowires in solar cell and light emitting devices. © 2010 American Institute of Physics. ͓doi:10.1063/1.3519980͔Semiconducting nanowires ͑NWs͒ are a topic of intense research as they offer the opportunity to explore properties of one-dimensional electronic systems. The understanding and the mastering of the electronic properties of such onedimensional systems are essential to achieve high efficiency devices. In particular, with the increase of the surface/volume ratio, the electronic properties of NW based devices become strongly dependent on the surface electronic states that can alter their electronic properties. Two main surface effects are reported in literature: surface states can act as recombination centers for free carriers 1,2 or as surface charged traps. 3,4 The first effect has recently been quantified by an original optical method for silicon NWs. 5,6 The surface charge traps induce a pinning of the Fermi-level at the surface. A depletion shell appears and the electronic channel available for carriers is narrowed. Experimental proof of this effect in semiconducting NWs was observed by photoconductivity or capacitancevoltage measurements. [7][8][9][10] In this letter, we present our results on the influence of surfaces on GaAs NWs measured by low temperature microphotoluminescence ͑-PL͒ spectroscopy. A systematic comparison is done between unpassivated NWs and those that were capped with a shell of Al 0.4 Ga 0.6 As. Moreover, we take advantage of the tapered shape of the NWs to understand the role of diameter and surface/volume ratios in the luminescence efficiency. We demonstrate that capping directly modifies the recombination velocity and that passivated NW electronic properties are governed by surface recombinations, whereas, unpassivated NWs are strongly depleted by the Fermi-level pinning at the surface induced by charged surface trap states. This work will serve as a guidance for the passivation of the NW surfaces, which is of crucial importance for applications in laser and solar cell technology. 11GaAs NWs were synthesized by molecular beam epitaxy. The growth conditions are described elsewhere. 12-14The NWs have a prismatic shape and exhibit a pure zincblende GaAs crystal structure oriented along the ͑111͒ direction. Surfaces are ͕110͖ oriented. 15,16 The NWs are extremely long ͑16 m͒ and present a tapered shape ͑diameters go from 140 nm at the base to 70 nm at the tip͒. We investigated two samples which di...

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“…The first hypothesis is a decrease of the minority carrier lifetime of the nanowire compared to the substrate [2] …”

Section: Resultsmentioning

confidence: 99%

“…The operation of nanowire based devices is then very dependent on the quality of the nanowires and their interfaces, thus the characterization of interfaces becomes challenging. The carrier lifetime of bottom-up nanowires has been characterized by photoconductivity [1], photoluminescence (PL) [2], or scanning photocurrent microscopy (SPCM) [3]. In this article, the reverse recovery transient (RRT) [4] is used to perform measurements on p-n heterojunctions under dark conditions.…”

Section: Introductionmentioning

confidence: 99%

Minority Carrier Lifetime Measurement in Nanowire Based Solar Cells by a Reverse Recovery Transient Method

et al. 2014

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Nanowire-based solar cells are interesting structures for photovoltaic applications as they enhance properties such as light absorption, trapping efficiency and carrier collection. Consequently, the potential to decrease the cost of photovoltaic energy thanks to these structures is not negligible. However, up to now, their efficiency has been limited mainly because of the recombination at the interfaces and in the volume. The effective minority carrier lifetime is a key parameter which is strongly connected to volume, interface and surface recombination properties. In this work, we have used a purely electrical approach called reverse recovery transient (RRT) to perform measurements of minority carrier lifetime in core-shell nanowire-based solar cells under dark conditions. The structures are based on crystalline silicon nanowires grown on silicon wafers and embedded in a radial amorphous silicon shell. The electrical contacts for this hetero-junction structure are transparent conductive oxide for the front surface and aluminum for the backside. A planar solar cell has also been fabricated to be used as a reference. By comparing RRT measurement on the nanowire-based solar cell and on the planar reference solar cell with simulations, we extract the lifetime of the nanowires.

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Surface Recombination Velocity Measurements of Efficiently Passivated Gold-Catalyzed Silicon Nanowires by a New Optical Method

Cited by 57 publications

References 28 publications

Geometrical control of photocurrent in active Si nanowire devices

Geometrical control of photocurrent in active Si nanowire devices

Impact of surfaces on the optical properties of GaAs nanowires

Minority Carrier Lifetime Measurement in Nanowire Based Solar Cells by a Reverse Recovery Transient Method

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