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Bandgap tuning of GaAs/GaAsSb core-shell nanowires grown by molecular beam epitaxy
- Source :
- Semiconductor Science and Technology. 30:105036
- Publication Year :
- 2015
- Publisher :
- IOP Publishing, 2015.
-
Abstract
- Semiconductor nanowires have been identified as a viable technology for next-generation infrared (IR) photodetectors with improved detectivity and detection across a range of energies as well as for novel single-photon detection in quantum networking. The GaAsSb materials system is especially promising in the 1.3–1.55 μm spectral range. In this work we present band-gap tuning up to 1.3 μm in GaAs/GaAsSb core–shell nanowires, by varying the Sb content using Ga-assisted molecular beam epitaxy. An increase in Sb content leads to strain accumulation in shell manifesting in rough surface morphology, multifaceted growths, curved nanowires, and deterioration in the microstructural and optical quality of the nanowires. The presence of multiple PL peaks for Sb compositions ≥12 at.% and degradation in the nanowire quality as attested by broadening of Raman and x-ray diffraction peaks reveal compositional instability in the nanowires. Transmission electron microscope (TEM) images show the presence of stacking faults and twins. Based on photoluminescence (PL) peak energies and their excitation power dependence behavior, an energy-band diagram for GaAs/GaAsSb core–shell nanowires is proposed. Optical transitions are dominated by type II transitions at lower Sb compositions and a combination of type I and type II transitions for compositions ≥12 at.%. Type I optical transitions as low as 0.93 eV (1.3 μm) from the GaAsSb for Sb composition of 26 at.% have been observed. The PL spectrum of a single nanowire is replicated in the ensemble nanowires, demonstrating good compositional homogeneity of the latter. A double-shell configuration for passivation of deleterious surface states leads to significant enhancement in the PL intensity resulting in the observation of room temperature emission, which provides significant potential for further improvement with important implications for nanostructured optoelectronic devices operating in the near-infrared regime.
- Subjects :
- Materials science
Photoluminescence
Passivation
Band gap
business.industry
Nanowire
Condensed Matter Physics
Electronic, Optical and Magnetic Materials
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Semiconductor
Materials Chemistry
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Optoelectronics
Electrical and Electronic Engineering
business
Raman spectroscopy
Molecular beam epitaxy
Surface states
Subjects
Details
- ISSN :
- 13616641 and 02681242
- Volume :
- 30
- Database :
- OpenAIRE
- Journal :
- Semiconductor Science and Technology
- Accession number :
- edsair.doi...........cf2078ec0b2ee2d3565294336b55f800