Removal of Surface States and Recovery of Band-Edge Emission in InAs Nanowires through Surface Passivation

Sun, Min; Joyce, Hannah J.; Gao, Qiang; Tan, Hark Hoe; Jagadish, Chennupati; Ning, Chao

doi:10.1021/nl300015w

Cited by 104 publications

(110 citation statements)

References 45 publications

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“…In the present study, we explore the use of surfactant (sulfur) for the CVD growth of NWs in order to achieve very thin GaSb NWs with the diameter down to 20 nm. In contrast to the surfactant effect typically reported in the liquid phase [22][23][24][25][26][27] (for example, solvothermal and hydrothermal) and thin-film technologies 28 , the sulfur atoms, commonly used for the surface passivation of III-V semiconductors [29][30][31][32] , are contributed to form S-Sb bonds on the as-grown NW surface, effectively stabilizing the sidewalls and thus minimizing the unintentional radial growth. Importantly, the obtained NWs are highly stoichiometric, single-crystalline with a smooth surface and very uniform in diameter without any tapering.…”

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confidence: 94%

Surfactant-assisted chemical vapour deposition of high-performance small-diameter GaSb nanowires

et al. 2014

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Although various device structures based on GaSb nanowires have been realized, further performance enhancement suffers from uncontrolled radial growth during the nanowire synthesis, resulting in non-uniform and tapered nanowires with diameters larger than few tens of nanometres. Here we report the use of sulfur surfactant in chemical vapour deposition to achieve very thin and uniform GaSb nanowires with diameters down to 20 nm. In contrast to surfactant effects typically employed in the liquid phase and thin-film technologies, the sulfur atoms contribute to form stable S-Sb bonds on the as-grown nanowire surface, effectively stabilizing sidewalls and minimizing unintentional radial nanowire growth. When configured into transistors, these devices exhibit impressive electrical properties with the peak hole mobility of B200 cm 2 V À 1 s À 1 , better than any mobility value reported for a GaSb nanowire device to date. These factors indicate the effectiveness of this surfactant-assisted growth for high-performance small-diameter GaSb nanowires.

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confidence: 94%

Surfactant-assisted chemical vapour deposition of high-performance small-diameter GaSb nanowires

et al. 2014

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“…These phase-pure nanowires have since been used to study how crystal phase influences the electronic [11,12], optical [13] and thermal properties [14].…”

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confidence: 99%

The influence of atmosphere on the performance of pure-phase WZ and ZB InAs nanowire transistors

et al. 2017

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Abstract. We compare the characteristics of phase-pure MOCVD grown ZB and WZ InAs nanowire transistors in several atmospheres: air, dry pure N 2 and O 2 , and N 2 bubbled through liquid H 2 O and alcohols to identify whether phase-related structural/surface differences affect their response. Both WZ and ZB give poor gate characteristics in dry state. Adsorption of polar species reduces off-current by 2 − 3 orders of magnitude, increases on-off ratio and significantly reduces sub-threshold slope. The key difference is the greater sensitivity of WZ to low adsorbate level. We attribute this to facet structure and its influence on the separation between conduction electrons and surface adsorption sites. We highlight the important role adsorbed species play in nanowire device characterisation. WZ is commonly thought superior to ZB in InAs nanowire transistors. We show this is an artefact of the moderate humidity found in ambient laboratory conditions: WZ and ZB perform equally poorly in the dry gas limit yet equally well in the wet gas limit. We also highlight the vital role density-lowering disorder has in improving gate characteristics, be it stacking faults in mixed-phase WZ or surface adsorbates in pure-phase nanowires.

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“…The charged surface states produce a random spatial electrostatic potential in the nanowire, which may contribute to the spontaneous formation of quantum dots at low temperature 9 . These states can also quench intrinsic photoluminescence, severely limiting the performance of optoelectronic devices 4,10 . Surface passivation should reduce the density of ionized surface states and lead to improved electron mobility.…”

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confidence: 99%

“…Growth of an InP shell on an InAs core 11 has been shown to yield better mobilities, as well as chemical passivation based on In-S bonding 10,12,13 . Here we study the effects of surface passivation due to an epitaxial In 0.8 Al 0.2 As shell.…”

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Electron transport in InAs-InAlAs core-shell nanowires

Holloway

Song

Haapamaki

et al. 2013

Applied Physics Letters

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Evidence is given for the effectiveness of InAs surface passivation by the growth of an epitaxial In 0.8 Al 0.2 As shell. The electron mobility is measured as a function of temperature for both core-shell and unpassivated nanowires, with the core-shell nanowires showing a monotonic increase in mobility as temperature is lowered, in contrast to a turnover in mobility seen for the unpassivated nanowires. We argue that this signifies a reduction in low temperature ionized impurity scattering for the passivated nanowires, implying a reduction in surface states. Core-shell nanowires were grown in a gas source molecular beam epitaxy system using Au seed particles 16 . First, InAs cores were grown axially by the Au assisted vapour liquid solid mechanism on a p-GaAs (111)B substrate at a growth temperature of 420This was followed by the inclusion of Al to facilitate radial growth of the In 0.8 Al 0.2 As shell 17 .The nanowires were characterized using transmission electron microscopy (TEM).As-grown nanowires were sonicated and suspended in ethanol, dispersed onto TEM grids have an inner core and an outer shell structure. In general, the nanowires had a core diameter of 20-50 nm and a shell that was 12-15 nm thick, independent of core diameter. The chemical composition of the nanowires was analyzed by energy-dispersive x-ray spectroscopy (EDS). As shown in Figure 1a, the EDS line scan analysis along the radial direction showsIn and As in the core region and In, As and Al in the shell region. High-resolution TEM (HRTEM) image of a representative unetched nanowire in Figure 1b clearly shows lattice 3 fringes of a single-crystal nanowire along the [2110] zone axis. Both core and shell exhibit wurtzite crystal structure, evidenced by ABAB... stacking, and confirmed by selected area diffraction. HRTEM and electron diffraction data are both consistent with a dislocation-free core-shell interface for these nanowires. However, at higher Al concentrations, dislocations due to relaxation of the core-shell interface are observed 17 . The nanowires studied here had low stacking fault densities, achieved by using sufficiently low growth rates 17,18 . Below, we also show data from unpassivated InAs nanowires that were grown under nominally identical conditions to the growths of the nanowire cores mentioned previously, except that the axial growth rate was 0.25 µm/hr and 0.5 µm/hr for the core-shell and bare nanowires, respectively.FET devices were fabricated using a standard e-beam lithography technique. As-grown nanowires were mechanically deposited onto a 175 nm thick SiO 2 layer above a n ++ -Si substrate. Selected nanowires with diameters 40−80nm were located relative to pre-existing fiducial markers by scanning electron microscopy (SEM), with care taken to minimize the electron dose. The contact areas were etched with citric acid to remove the shell material, followed by room temperature sulfur passivation to prevent oxide regrowth 19 during the sample transfer to an e-beam metal evaporator. Ni/Au (30nm/50nm) metal contacts were...

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Removal of Surface States and Recovery of Band-Edge Emission in InAs Nanowires through Surface Passivation

Cited by 104 publications

References 45 publications

Surfactant-assisted chemical vapour deposition of high-performance small-diameter GaSb nanowires

Surfactant-assisted chemical vapour deposition of high-performance small-diameter GaSb nanowires

The influence of atmosphere on the performance of pure-phase WZ and ZB InAs nanowire transistors

Electron transport in InAs-InAlAs core-shell nanowires

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