English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

A study of the Fermi-energy edge singularity (FEES) in the second (n=2) subband of asymmetric modulation-doped (AlGa)As-(InGa)As-GaAs quantum wells (AMDQW's) is reported. In one of the AMDQW's a Schottky gate is employed to vary the electron density in the n=2 subband (${\mathit{n}}_{\mathit{s},2}$) from 0 to 1\ifmmode\times\else\texttimes\fi{}${10}^{11}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$. Temperature-dependent photoluminescence excitation (PLE) measurements clearly show that the n=2 PLE feature has FEES character for ${\mathit{n}}_{\mathit{s},2}$\ensuremath{\gtrsim}0.4\ifmmode\times\else\texttimes\fi{}${10}^{11}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$. In contrast to PLE, photoluminescence (PL) intensity is not a true measure of oscillator strength, since PL intensity can be affected by competing recombination pathways. Temperature-dependent PL measurements have been performed on two types of AMDQW. One type has ${\mathit{n}}_{\mathit{s},2}$\ensuremath{\sim}0, with the Fermi energy close to the n=2 subband energy. The other type has ${\mathit{n}}_{\mathit{s},2}$=1\ifmmode\times\else\texttimes\fi{}${10}^{11}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ and a FEES associated with n=2 observed in PLE. We demonstrate that the very similar broadening and reduction in peak height of the n=2 PL peak with temperature for the two types of samples can be accounted for in terms of spreading of the electron or exciton populations near the n=2 subband edge. Therefore, we conclude that temperature-dependent PL does not provide unequivocal evidence for a many-body enhancement of the n=2 PL transition, in contrast to that reported by Chen et al. [Phys. Rev. Lett. 64, 2434 (1990)].

Fermi-energy edge singularity and excitonic enhancement associated with the second subband in asymmetric modulation-doped quantum wells