Value and Anisotropy of the Electron and Hole Mass in Pure Wurtzite InP Nanowires.
The effective mass of electrons and holes in semiconductors is pivotal in determining the dynamics of carriers and their confinement energy in nanostructured materials. Surprisingly, this quantity is still unknown in wurtzite (WZ) nanowires (NWs) made of III-V compounds (e.g., GaAs, InAs, GaP, InP), where the WZ phase has no bulk counterpart. Here, we investigate the magneto-optical properties of InP WZ NWs grown by selective-area epitaxy that provides perfectly ordered NWs featuring high-crystalline quality. The combined analysis of the energy of free exciton states and impurity levels under magnetic field (B up to 29 T) allows us to disentangle the dynamics of oppositely charged carriers from the Coulomb interaction and thus to determine the values of the electron and hole effective mass. By application of B⃗ along different crystallographic directions, we also assess the dependence of the transport properties with respect to the NW growth axis (namely, the WZ ĉ axis). The effective mass of electrons along ĉ is me∥= (0.078 ± 0.002) m0(m0is the electron mass in vacuum) and perpendicular to ĉ is me⊥= (0.093 ± 0.001) m0, resulting in a 20% mass anisotropy. Holes exhibit a much larger (∼320%) and opposite mass anisotropy with their effective mass along and perpendicular to ĉ equal to mh∥= (0.81 ± 0.18) m0and mh⊥= (0.250 ± 0.016) m0, respectively. While no full consensus is found with current theoretical results on WZ InP, our findings show trends remarkably similar to the experimental data available in WZ bulk materials, such as InN, GaN, and ZnO.
Dipartimento di Fisica, Sapienza Università di Roma , Piazzale A. Moro 2, 00185 Roma, Italy.
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Tedeschi
Dipartimento di Fisica, Sapienza Università di Roma , Piazzale A. Moro 2, 00185 Roma, Italy.
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De Luca
High Field Magnet Laboratory (HFML - EMFL), Radboud University , Toernooiveld 7, NL-6525 ED Nijmegen, The Netherlands.
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Granados Del Águila
Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University , Canberra, ACT 2601, Australia.
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Gao
Dipartimento di Fisica, Sapienza Università di Roma , Piazzale A. Moro 2, 00185 Roma, Italy.
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Ambrosio
Dipartimento di Fisica, Sapienza Università di Roma , Piazzale A. Moro 2, 00185 Roma, Italy.
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Capizzi
Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University , Canberra, ACT 2601, Australia.
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Tan
High Field Magnet Laboratory (HFML - EMFL), Radboud University , Toernooiveld 7, NL-6525 ED Nijmegen, The Netherlands.
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Christianen
Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University , Canberra, ACT 2601, Australia.
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Jagadish
Dipartimento di Fisica, Sapienza Università di Roma , Piazzale A. Moro 2, 00185 Roma, Italy.
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Polimeni
Wurtzite InP nanowires; carrier effective mass; excitons; impurity states; magneto-photoluminescence