Photoluminescence spectroscopy of crystalline semiconductors

Long exciton lifetimes in stacking-fault-free wurtzite GaAs nanowires

“…17 The measured decay time is also longer than intrinsic exciton recombination lifetimes in pure ZB structures like bulk GaAs and 2D GaAs/AlGaAs wide double heterostructures. 30 Note that our experiment gives the lower limit, as the observed PL lifetime can be expected to be shortened by non-radiative recombination channels at the GaAs/AlGaAs core-shell interface. 23,34 In general, long excitonic lifetimes in NWs have been attributed to local charge separation induced by crystal phase mixing.…”

“…2(a) have energies smaller than the free exciton recombination in ZB GaAs (E ¼ 1.515 eV). 30 A l-PL spectrum recorded at the position marked with the dashed line is depicted in Fig. 2(b).…”

Photocatalytic Semiconductors

“…Thus, this characterization technique can give direct information on electron transfer kinetics during the photocatalytic process. The PL intensity can be used to compare recombination rates for different photocatalytic systems, detect impurities and defects in the sample, and estimate the band gap through the band to band transitions (Anpo et al 2009;Gilliand 1997), as it is shown in Fig. 4.23 for a photocatalytic ZnO film.…”

Measuring the Energy Landscape in Single Semiconductor Nanowires

“…A laser which emits photons with energy larger than the energy gap is used to excite electronhole pairs high up into the valence and conduction bands of a semiconductor nanostructure. The electrons and holes rapidly thermalize within a picosecond to the lowest energy states within the nanostructure, and may then emit light which is characteristic of thisnal state [15]. Using a high quality microscope objective one can couple light which is emitted from a single nanostructure (or even from a small section of a nanowire) to a spectrometer and imaging detector.…”

“…The most sensitive and accurate technique using PL to measure excited states in single nanostructures is to use photoluminescence excitation (PLE) spectroscopy [15]. Here the emission intensity from a ground state or defect level is monitored as an excitation laser is tuned to higher energies.…”