We report on a major modification of the fundamental electronic band structure of AlAs when grown as a nanoscaled wurtzite crystal. Resonant Raman spectra of individual AlAs-GaAs core-shell nanowires display a resonance between 1.83 and 2.18 eV for the AlAs E₁(TO) phonon mode. Our findings substantiate the lowest conduction band of wurtzite AlAs to comprise Γ₈ symmetry and a low effective mass in agreement with calculations reported recently. The electronic resonance falls below the X, L, and Γ valleys known for AlAs in the zincblende phase. This result points toward a direct nature of wurtzite AlAs and is expected to apply more generally to semiconductors that in the bulk phase exhibit L valleys at lower energies than the conduction band at the Γ point.

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http://dx.doi.org/10.1021/nn305112aDOI Listing

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