Publication

Charge carrier generation, relaxation, and recombination in polytypic GaAs nanowires studied by photoluminescence excitation spectroscopy

Abstract

We report results of a study of polytypic GaAs nanowires using low-temperature photoluminescence excitation spectroscopy. The nanowire ensemble shows a strong absorption at 1.517 eV, as a result of resonant generation of heavy-hole excitons in the zinc-blende segments of the nanowires. Excitons then diffuse along the length of the nanowire and are trapped by the type-II quantum discs arising from the zinc-blende/ wurtzite crystal structure alternation and recombine radiatively. Finally, experiments on single nanowires demonstrate that the energy of the Gamma(7) conduction band to Gamma(9) valence band exciton of wurtzite GaAs is 1.521 eV at 4K. (C) 2013 AIP Publishing LLC.

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Related concepts (30)
Valence and conduction bands
In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level, and thus determine the electrical conductivity of the solid. In nonmetals, the valence band is the highest range of electron energies in which electrons are normally present at absolute zero temperature, while the conduction band is the lowest range of vacant electronic states. On a graph of the electronic band structure of a semiconducting material, the valence band is located below the Fermi level, while the conduction band is located above it.
Exciton
An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids. The exciton is regarded as an elementary excitation of condensed matter that can transport energy without transporting net electric charge. An exciton can form when a material absorbs a photon of higher energy than its bandgap. This excites an electron from the valence band into the conduction band.
Band gap
In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the energy difference (often expressed in electronvolts) between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is the energy required to promote an electron from the valence band to the conduction band.
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