Non-thermal photoexcited electron distributions in non-stoichiometric GaAs

Abstract

We present experimental evidence of inverted photoluminescence spectra in GaAs. The spectra are measured for As-rich GaAs layers with ultrashort (of the order of 30-60 fs) carrier lifetimes. Ensemble Monte Carlo simulations performed using the molecular dynamics approach confirm that the observed PL spectra are generated by non-thermalized carriers several tens of femtoseconds after their excitation.

Semiconductors for terahertz photonics applications

“…Similar result (τ l~7 0 fs) has been obtained also after a quantitative comparison of the measured PL spectrum with the results of the numerical simulation by a combined Monte Carlo / molecular dynamics procedure [70]. Figure 11 shows a collection of electron lifetimes in the LTG GaAs grown at different temperatures and annealed at 600 o C [61,65,[70][71][72]. The available experimental data for the as-grown LTG GaAs [61,70] are also presented for comparison.…”

“…In [70] the electron trapping time in asgrown LTG GaAs was determined indirectly, by investigating the photoluminescence (PL) spectra.…”

“…By interpolating the missing parts of the spectra and by assuming that the matrix elements for the radiative recombination for the as-grown and the annealed samples are the same, the carrier lifetime for as-grown LTG GaAs of about 60 fs has been deduced [70]. Similar result (τ l~7 0 fs) has been obtained also after a quantitative comparison of the measured PL spectrum with the results of the numerical simulation by a combined Monte Carlo / molecular dynamics procedure [70]. Figure 11 shows a collection of electron lifetimes in the LTG GaAs grown at different temperatures and annealed at 600 o C [61,65,[70][71][72].…”

Semiconductor materials for ultrafast optoelectronic applications

“…In as-grown LTG GaAs layers, the electrons are trapped on a time scale shorter than 100 fs, therefore this dynamics is impossible to investigate by using standard pump-and-probe techniques. In [14] we studied electron trapping in as-grown LTG GaAs indirectly, by investigating PL spectral dependences. Because photo-excited electrons in this material are captured by the trapping centres faster than they reach thermal distribution, the photoluminescence spectrum is peaking not at the vicinity of the band-edge energy (∼1.4 eV for GaAs) but around the photoexcitation energy.…”

Mesures et modélisations d'effets de saturation dans un photocommutateur picoseconde en GaAs BT

“…Pour cela, on utilise des matériaux semi-conducteurs possédant une grande densité de défauts qui servent à piéger très efficacement les charges photogénérées. Ainsi, la durée de vie des électrons peut être inférieure à 100 fs [1] dans des matériaux non stoechiométriques comme GaAs épitaxié à basse température (LT-GaAs), où un excès d'arsenic forme des défauts de type antisite. Cependant, la réponse du détecteur n'est pas seulement déterminée par la réponse du matériau, mais aussi par celle du circuit hyperfréquences.…”