Aluminum-Induced Photoluminescence Red Shifts in Core–Shell GaAs/AlxGa1–xAs Nanowires

Dhaka, Veer; Oksanen, Jani; Jiang, Hua; Haggrén, Tuomas; Nykänen, Antti; Sanatinia, Reza; Kakko, Joona-Pekko; Huhtio, Teppo; Mattila, Marco; Ruokolainen, Janne; Anand, Srinivasan; Kauppinen, Esko I.; Lipsanen, Harri

doi:10.1021/nl4012613

Cited by 26 publications

(35 citation statements)

References 27 publications

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“…In addition, Al-rich bands at the corners of the six hexagonal {110} sidewall facets could be observed [177]. Such Al-rich bands have previously been observed for both Au- [178][179][180][181] and self-catalyzed [182,183] GaAs/AlGaAs core-shell NWs as well as Au-catalyzed GaAs/AlInP coreshell NWs [184,185], indicating that the elemental enrichment is a universal phenomenon. These phenomena are in agreement with the self-ordering of nanostructures on non-planar surfaces observed by Biasiol et al and have been associated with the difference in the chemical potential and adatoms diffusivity on {110} and {112} type surfaces [186][187][188].…”

Section: Optical Propertiesmentioning

confidence: 62%

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Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography

et al. 2014

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This thesis deals with the growth of GaAs nanowires (NWs) by molecular beam epitaxy (MBE) using vapor-liquid-solid method on various substrates including GaAs(111)B, Si(111) and graphene. The growth of the NWs on GaAs substrates was carried out by Au-catalyzed technique, whereas the growths on Si and graphene substrates were carried out using self-catalyzed technique that has been the main focus of this thesis. The long-term goal of this work was to produce p-n radial junction GaAs NWs for solar cell applications.Necessary conditions were established for obtaining vertical self-catalyzed GaAs NWs on Si(111), which is reproducible from run-to-run. One of the major issues in these NWs grown by both Au-and self-catalyzed techniques is their crystal structure. The Au-catalyzed GaAs NWs usually adopt a wurtzite (WZ) crystal phase, whereas the self-catalyzed NWs a zinc blende (ZB) phase. However, in both the cases the NWs contain stacking faults, rotational twins or/and a mixed crystal phase. The ZB and WZ phases show different optical properties, and one phase might be favored over other for certain applications. Therefore the crystal phase was controlled within single NWs by tuning the V/III ratio and introducing GaAsSb inserts. The change of the crystal phases was correlated with the change in the contact angle of the Ga droplet.Since the discovery of graphene, an ultra-thin two-dimensional material, the research on graphene has become an active field in recent years due to its remarkable properties including excellent electrical and thermal conductivities, mechanical strength and flexibility, and optical transparency. By growing the semiconductor NWs on graphene, a completely new hybrid system can be envisioned where the unique properties of both NWs and graphene can be utilized. Therefore we established a method for the growth of semiconductor NWs on graphene by demonstrating epitaxial growth of vertical GaAs and InAs NWs on different graphitic substrates.Core-shell heterostructure, doping, optical properties, and position controlled growth of self-catalyzed GaAs NWs were investigated. Growth of GaAs/GaAsSb coreshell NWs where the Sb content was tuned from about 10% -70% was studied. The effect of growth temperature and the Sb flux on the morphology of GaAsSb shell was investigated. In addition, by utilizing the core-shell geometry where the shell copies the crystal phase of the core, WZ phase of GaAsSb was demonstrated. Successful p-type doping of GaAs core using Be as dopant, and n-type doping of GaAs shell using Si and Te as dopants were achieved. To investigate the optical properties, GaAs/AlGaAs coreshell NWs were grown with different V/III ratios during the core growth. The NWs grown with high V/III ratio, despite containing a higher density of twinned ZB and WZ GaAs with SFs, were found to have superior optical quality as compared to the NWs grown with low V/III ratio that contain pure ZB GaAs. The observed V/III ratio dependent optical quality was correlated to the intrinsic defects such as As vac...

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Section: Optical Propertiesmentioning

confidence: 62%

“…Recently, the effect of strain from the AlGaAs shell on the GaAs core was studied. Increasing the Al content as well the thickness of the AlGaAs shell were reported to redshift the PL peak from the GaAs core [196,197]. Therefore, a separate study should be carried out for MBE grown NWs by varying the Al content and the shell thickness.…”

Section: Discussionmentioning

confidence: 99%

Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography

et al. 2014

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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.…”

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confidence: 91%

“…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.…”

Section: Introductionmentioning

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.…”

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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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Enhanced photocurrent and photoluminescence spectra in MoS2 under ionic liquid gating

Chang

Chen

et al. 2014

Nano Res.

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Aluminum-Induced Photoluminescence Red Shifts in Core–Shell GaAs/Al_xGa_1–xAs Nanowires

Cited by 26 publications

References 27 publications

Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography

Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography

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

Enhanced photocurrent and photoluminescence spectra in MoS2 under ionic liquid gating

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