Determination of the band gap and the split-off band in wurtzite GaAs using Raman and photoluminescence excitation spectroscopy

Ketterer, Bernt; Heiß, Martin; Livrozet, Marie J.; Rudolph, Andreas; Reiger, Elisabeth; Morral, Anna Fontcuberta i

doi:10.1103/physrevb.83.125307

Cited by 65 publications

(65 citation statements)

References 42 publications

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“…The crystal field splitting and spin-orbit splitting of the unstrained nanowires are found to be D CR ¼ 197 meV±50 meV and D SO ¼ 293 meV ± 129 meV, respectively. Both of these values agree well with other experimental results 41,42 (D SO ¼ 379 meV) and theoretical predictions (the crystal field splitting ranges from 180 meV to 212 meV between different ab-initio methods). The WZ GaAs k Á p model can therefore explain all optical transitions observed in our experiment, with the exception of the photons identified by the yellow peak in Fig 5. Further investigations are needed to elucidate the nature of these peaks and are currently ongoing.…”

Section: Articlesupporting

confidence: 91%

Inducing a direct-to-pseudodirect bandgap transition in wurtzite GaAs nanowires with uniaxial stress

et al. 2014

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Many efficient light-emitting devices and photodetectors are based on semiconductors with, respectively, a direct or indirect bandgap configuration. The less known pseudodirect bandgap configuration can be found in wurtzite (WZ) semiconductors: here electron and hole wave-functions overlap strongly but optical transitions between these states are impaired by symmetry. Switching between bandgap configurations would enable novel photonic applications but large anisotropic strain is normally needed to induce such band structure transitions. Here we show that the luminescence of WZ GaAs nanowires can be switched on and off, by inducing a reversible direct-to-pseudodirect band structure transition, under the influence of a small uniaxial stress. For the first time, we clarify the band structure of WZ GaAs, providing a conclusive picture of the energy and symmetry of the electronic states. We envisage a new generation of devices that can simultaneously serve as efficient light emitters and photodetectors by leveraging the strain degree of freedom.

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Section: Articlesupporting

confidence: 91%

Inducing a direct-to-pseudodirect bandgap transition in wurtzite GaAs nanowires with uniaxial stress

et al. 2014

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“…Experimental results showed the bandgap of WZ phase is larger than that of ZB for GaAs [111][112][113], as well as for other material systems [114,115]. However for GaAs, contrary reports showing a smaller bandgap of the WZ phase than the ZB phase are also available [112,116,117]. In addition to the differences in the bandgap, the linear polarization of the PL emission was found to be strongly dependent on the crystal phase of the NWs.…”

Section: Extended Defectsmentioning

confidence: 70%

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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“…For transition C, full circles refer to data extracted using a best fit to PLE spectra, and open squares refer to data extracted by employing F abs in panel (a) and the graphical method outlined in Figure 6 (b 20 Moreover, our results differ from resonant Raman scattering measurements performed on WZ GaAs NWs indicating that the T-induced redshift of transition C is greater than that of the band gap in ZB GaAs. 39 Our findings clearly show that the main mechanisms ruling the extent of the band gap variation with temperature, namely, the lattice expansion and the electronÀphonon interaction, do not depend on the NW crystal phase. Indeed, in both ZB and WZ phases of a binary compound, which we can indicate as AB, four A atoms nearest neighbors of a B atom are placed at the vertices of a regular tetrahedron around the B atom and nine out of the 12 second nearest neighbors are at identical crystallographic locations while the other second nearest neighbors are equidistant.…”

Section: Articlementioning

confidence: 89%

Temperature Dependence of Interband Transitions in Wurtzite InP Nanowires

et al. 2015

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Semiconductor nanowires (NWs) formed by non-nitride III-V compounds grow preferentially with wurtzite (WZ) lattice. This is contrary to bulk and two-dimensional layers of the same compounds, where only zincblende (ZB) is observed. The absorption spectrum of WZ materials differs largely from their ZB counterparts and shows three transitions, referred to as A, B, and C in order of increasing energy, involving the minimum of the conduction band and different critical points of the valence band. In this work, we determine the temperature dependence (T = 10-310 K) of the energy of transitions A, B, and C in ensembles of WZ InP NWs by photoluminescence (PL) and PL excitation (PLE) spectroscopy. For the whole temperature and energy ranges investigated, the PL and PLE spectra are quantitatively reproduced by a theoretical model taking into account contribution from both exciton and continuum states. WZ InP is found to behave very similarly to wide band gap III-nitrides and II-VI compounds, where the energy of A, B, and C displays the same temperature dependence. This finding unveils a general feature of the thermal properties of WZ materials that holds regardless of the bond polarity and energy gap of the crystal. Furthermore, no differences are observed in the temperature dependence of the fundamental band gap energy in WZ InP NWs and ZB InP (both NWs and bulk). This result points to a negligible role played by the WZ/ZB differences in determining the deformation potentials and the extent of the electron-phonon interaction that is a direct consequence of the similar nearest neighbor arrangement in the two lattices.

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Determination of the band gap and the split-off band in wurtzite GaAs using Raman and photoluminescence excitation spectroscopy

Cited by 65 publications

References 42 publications

Inducing a direct-to-pseudodirect bandgap transition in wurtzite GaAs nanowires with uniaxial stress

Inducing a direct-to-pseudodirect bandgap transition in wurtzite GaAs nanowires with uniaxial stress

Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography

Temperature Dependence of Interband Transitions in Wurtzite InP Nanowires

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