Determination of the Optimal Shell Thickness for Self-Catalyzed GaAs/AlGaAs Core–Shell Nanowires on Silicon

Songmuang, R.; Giang, Lê Thuy Thanh; Bleuse, J.; Hertog, M. den; Niquet, Yann-Michel; Dang, Le Si; Mariette, H.

doi:10.1021/acs.nanolett.5b03917

Cited by 23 publications

(29 citation statements)

References 48 publications

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“…However, for the passivated NW surface with S ≤ 1 × 10 4 cm/s and N TD = N TA = 1 × 10 12 /cm 2 surface recombination does not lead to severe efficiency decrease. Such high quality nanowire surfaces were already achieved for passivated GaAs nanowires [20,42], and should be used in high efficiency nanowire solar cells. Finally, it was shown that surface defects do not directly severely alter the current-matching condition as long as the p − n junction shell stays in the proper partially depleted regime.…”

Section: Surface Recombinationmentioning

confidence: 98%

Technological guidelines for the design of tandem III-V nanowire on Si solar cells from opto-electrical simulations

Maryasin

Bucci

Rafhay

et al. 2017

Solar Energy Materials and Solar Cells

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Effect of geometrical and structural parameters on the efficiency of the tandem solar cell based on the III-V nanowire array on silicon is studied by the means of coupled opto-electrical simulations. A close to realistic structure, consisting of AlGaAs core-shell nanowire array, connected through a tunnel diode to a Si subcell is modelled, revealing the impact of top contact layer, growth mask and tunnel junction. Optical simulation of the tandem structure under current matching condition determine optimal geometrical parameters of the nanowire array. They are then used in the extensive electrical optimization of the radial junction in the nanowire subcell. Device simulations show the necessity of high doping of the junction in order to avoid full shell depletion. The influence of bulk and surface recombination on the performance of the top subcell is studied, exposing the importance of the good surface passivation near the depleted region of the radial p − n junction. Finally, simulations of the fully optimized tandem structure show that a promising efficiency of η = 27.6% with the short-circuit current of J SC = 17.1 mA/cm 2 can be achieved with reasonable bulk and surface carrier lifetime.

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Section: Surface Recombinationmentioning

confidence: 98%

Technological guidelines for the design of tandem III-V nanowire on Si solar cells from opto-electrical simulations

Maryasin

Bucci

Rafhay

et al. 2017

Solar Energy Materials and Solar Cells

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“…24 This discrepancy can be partly ascribed to the MetalOrganic Vapor Phase Epitaxy The small blue shift observed at low powers, which saturates around 10µW has been also observed for GaAs nanowires capped with AlGaAs shell 26,27 and it was associated with the presence of some negatively charged traps at the interface, which are filled by photo created carriers in the AlGaAs shell, which migrates towards interface. Once filled, they can no longer modify the band bending at the interface, which explains the saturation of the blue-shift of the emission energy above 10µW, indicating that the band bending is the dominant effect in our nanomembranes.…”

mentioning

confidence: 89%

“…Several effects have been reported, such as band bending at the interface leading to the accumulation of the charge at the interface or piezo electric strain. [23][24][25][26][27] In addition, the AlGaAs alloy typically used for capping GaAs nanowires is generally inhomogeneous, with directed and random segregation of Ga and Al forming respectively Al-rich ridges and Ga-rich nanoscale islands . 28,29 Simultaneously, III-V NWs can suffer from twin defects and polytypism, 30,31 which adversely affect their electronic and optical properties.…”

mentioning

confidence: 99%

“…In fact, a similar effect has been observed previously for a simple AlGaAs/GaAs interface, 23,49 InP nanowires, 50 and for GaAs nanowires capped with AlGaAs shell . 24,26,27 For simple AlGaAs/GaAs the band bending at the interface forms a pocket for the electrons or holes . 23,49 Such confined carriers at the interface will recombine with the free carriers (of the opposite species) in the valence or conduction band at a sufficient distance from the interface that flat-band conditions have been re-established.…”

mentioning

confidence: 99%

“…50 Finally, for GaAs nanowires capped with AlGaAs shell, the mechanism of the band bending can be enriched by strain, related to the shell thickness. 26,27 However, the strain plays a significant role only for rather thick shells. In the case of the nano membranes the core is much thicker than the shell.…”

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confidence: 99%

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Revealing Large-Scale Homogeneity and Trace Impurity Sensitivity of GaAs Nanoscale Membranes

et al. 2017

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III-V nanostructures have the potential to revolutionize optoelectronics and energy harvesting. For this to become a reality, critical issues such as reproducibility and sensitivity to defects should be resolved. By discussing the optical properties of MBE grown GaAs nanomembranes we highlight several features that bring them closer to large scale applications. Uncapped membranes exhibit a very high optical quality, 1 arXiv:1704.08477v1 [cond-mat.mes-hall] 27 Apr 2017 expressed by extremely narrow neutral exciton emission, allowing the resolution of the more complex excitonic structure for the first time. Capping of the membranes with an AlGaAs shell results in a strong increase of emission intensity but also to a shift and broadening of the exciton peak. This is attributed to the existence of impurities in the shell, beyond MBE-grade quality, showing the high sensitivity of these structures to the presence of impurities. Finally, emission properties are identical at the sub-micron and sub-millimeter scale, demonstrating the potential of these structures for large scale applications.Keywords: GaAs/AlGaAs nano mebranes, photoluminescence, electronic and optical properties of ensemble vs single nano membrane Nanowires (NWs) are filamentary crystals with a diameter in the sub-micrometer down to nanometer range. Their special morphology, dimensions and high surface-to-volume ratio are often translated into advantageous optical and electrical properties. As a consequence, they have been widely used in electronics, 1-5 optoelectronics, 6,7 solar cells 8-11 and sensors. 12,13 If not adequately passivated, the surface recombination can limit the optical performance of the NWs. 14 In addition, surface depletion can also affect the volume distribution and separation of the carriers in the NW. 15-19 Different passivation methods have been employed in the past, notably capping of the free surfaces with a higher bandgap shell around the nanowire. [20][21][22] Nevertheless, capping also modifies the nature of the surface. Several effects have been reported, such as band bending at the interface leading to the accumulation of the charge at the interface or piezo electric strain. [23][24][25][26][27] In addition, the AlGaAs alloy typically used for capping GaAs nanowires is generally inhomogeneous, with directed and random segregation of Ga and Al forming respectively Al-rich ridges and Ga-rich nanoscale islands . 28,29 Simultaneously, III-V NWs can suffer from twin defects and polytypism, 30,31 which adversely affect their electronic and optical properties. 32-34 With a judicious optimization of growth conditions, single NWs with a pure zinc-blende or wurzite structure can be obtained. [35][36][37] Still, the optical and electronic properties tend to fluctuate considerably from NW to NW, 2 which precludes the proper control of the response of an ensemble of nanowires.Recently, alternative approaches to obtain defect-free nano structures have been proposed. Particularly promising is the inversion of polarity from B to A...

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Fe‐Doped p‐ZnO Nanostructures/n‐GaN Heterojunction for “Blue‐Free” Orange Light‐Emitting Diodes

Zhao

Xiong

Han

et al. 2017

Advanced Optical Materials

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In order to obtain the necessary band gap for light‐emitting diodes (LEDs) with zero emission at blue wavelengths (“blue‐free”), quasi‐3D nanostructures of p‐type Fe‐doped zinc oxide (ZnO:Fe) are fabricated on an n‐type GaN substrate. The ZnO:Fe nanostructure comprises an array of vertical nanowires attached at the nodes of a 2D network. Elemental analysis and field‐effect‐transistor (FET) and current–voltage (I–V) measurements indicate the successful iron‐doping of ZnO. After doping, the ZnO exhibits p‐type conductivity, a local‐charge‐reservoir layer, and an abundance of Fe‐related deep levels. The cathodoluminescence (CL), photoluminescence (PL) at various temperatures (down to 4.65 K), and electroluminescence (EL) confirm the creation of Fe‐related donor and acceptor levels. New donor levels may be attributed to the substitution of Fe for some Zn sites (“FeZn”), while new acceptor levels may be due to the bind of FeZn with Zn vacancies, (producing FeZn–VZn pairs). These doping‐induced energy levels are helpful in restricting the intrinsic ZnO UV and blue emission, and a stable blue‐free orange LED device is achieved. It has chromaticity coordinates of ∼(0.483, 0.447) and a color temperature of ∼2574 K under bias voltages of 6–16 V, making it potentially applicable to electronic display systems.

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Determination of the Optimal Shell Thickness for Self-Catalyzed GaAs/AlGaAs Core–Shell Nanowires on Silicon

Cited by 23 publications

References 48 publications

Technological guidelines for the design of tandem III-V nanowire on Si solar cells from opto-electrical simulations

Technological guidelines for the design of tandem III-V nanowire on Si solar cells from opto-electrical simulations

Revealing Large-Scale Homogeneity and Trace Impurity Sensitivity of GaAs Nanoscale Membranes

Fe‐Doped p‐ZnO Nanostructures/n‐GaN Heterojunction for “Blue‐Free” Orange Light‐Emitting Diodes

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