Interplay of exciton and electron-hole plasma recombination on the photoluminescence dynamics in bulk GaAs

Abstract

We present a systematic study of the exciton/electron-hole plasma photoluminescence dynamics in bulk GaAs for various lattice temperatures and excitation densities. The competition between the exciton and electron-hole pair recombination dominates the onset of the luminescence. We show that the metal-to-insulator transition, induced by temperature and/or excitation density, can be directly monitored by the carrier dynamics and the time-resolved spectral characteristics of the light emission. The dependence on carrier density of the photoluminescence rise time is strongly modified around a lattice temperature of 49 K, corresponding to the exciton binding energy (4.2 meV). In a similar way, the rise-time dependence on lattice temperature undergoes a relatively abrupt change at an excitation density of 120-180x10 15 cm -3 , which is about five times greater than the calculated Mott density in GaAs taking into account many body corrections.

Thermodynamic origin of the slow free exciton photoluminescence rise in GaAs

“…The Saha equation also predicts the existence of free excitons at k B T L 4.2 meV (the exciton binding energy) and therefore provides a natural alternative explanation to the formation of a Coulomb-correlated EHP for the presence of free exciton luminescence at elevated sample temperatures T L 48 K [13].…”

“…Time-resolved photoluminescence spectroscopy is widely used to investigate the kinetics of free exciton formation, relaxation, and recombination in semiconductors and their nanostructures [1]. In most experiments performed at low lattice temperatures a significantly delayed onset of the free exciton luminescence with respect to the excitation laser pulse is observed [2][3][4][5][6][7][8][9][10][11][12][13]. This slow photoluminescence (PL) rise has attracted intense research interest for nearly three decades.…”

“…the negligible emission intensity from direct band-to-band transitions in Fig. 1) and assume that n 0 (t) decays exclusively by the much more efficient channel of free exciton radiative decay [13,38]. The time evolution of the photocarrier pair density n 0 (t) is then described by the rate equation…”

Picosecond photoluminescence dynamics in an InGaAs/GaAs quantum-well heterostructure

“…It should be noted that, as the temperature is lowered, the cooling rate of The PL rise time in the vicinity of the basic e1-hh1 transition (at 1.319 eV, at T = 10 K) decreases from 21 to 6.4 ps, as the excitation power is increased from 1.35 to 180 mW. The profound decrease in the PL rise time with increasing excitation power is apparently due to competition of electron-hole recombination with excitonic recombination, as in [8]. Excitonic recombination prevails at low concentrations of charge carriers and can be characterized by a longer time of exciton formation because of the interaction of charge carriers with acoustic phonons.…”

Temperature dependence of the indirect bandgap in thallium bromide from cathodoluminescence spectroscopy

“…Finally, it is possible that the higher energy emission is associated with electron-hole plasma (EHP) emission, 24 although studies of the temperature dependence of EHP emission in GaAs show it following the bandgap variation. 25 Further studies will be required as a function of excitation energy on the 3.0 eV emission peak.…”