A Story Told by a Single Nanowire: Optical Properties of Wurtzite GaAs

• Published in: Nano letters Vol. 12; no. 12; pp. 6090 - 6095
• Main Authors: Ahtapodov, Lyubomir, Todorovic, Jelena, Olk, Phillip, Mjåland, Terje, Slåttnes, Patrick, Dheeraj, Dasa L, van Helvoort, Antonius T. J, Fimland, Bjørn-Ove, Weman, Helge
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 12.12.2012
• Subjects: Aluminum gallium arsenides; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electron states; Exact sciences and technology; Excitons and related phenomena; Gallium arsenide; Gallium arsenides; Materials science; Molecular beam epitaxy; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Nanowires; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Quantum wires; Scanning electron microscopy; Wurtzite; Zinc; optical properties; photoluminescence; Nanowires; wurtzite GaAs; TEM; Au-assisted MBE growth; Aluminium arsenides; Integrated intensity; Conduction bands; Gold; Gallium arsenides; Symmetry property; Brightness; Core shell structure; Photoluminescence; Aluminium Gallium Arsenides Mixed; Time resolved spectra; III-V compound; Zinc; Time resolution; Energy gap; Excitons; Optical properties; Molecular beam epitaxy; Scanning transmission electron microscopy; Nanostructured materials; III-V semiconductors
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl3025714

The optical properties of the wurtzite (WZ) GaAs crystal phase found in nanowires (NWs) are a highly controversial topic. Here, we study high-quality pure WZ GaAs/AlGaAs core–shell NWs grown by Au-assisted molecular beam epitaxy (MBE) with microphotoluminescence spectroscopy (μ-PL) and (scanning) transmission electron microscopy on the very same single wire. We determine the room temperature (294 K) WZ GaAs bandgap to be 1.444 eV, which is ∼20 meV larger than in zinc blende (ZB) GaAs, and show that the free exciton emission at 15 K is at 1.516 eV. On the basis of time- and temperature-resolved μ-PL results, we propose a Γ8 conduction band symmetry in WZ GaAs. We suggest a method for quantifying the optical quality of NWs, taking into consideration the difference between the room and low temperature integrated PL intensity, and demonstrate that Au-assisted GaAs/AlGaAs core–shell NWs can have high PL brightness up to room temperature.