Hopping relaxation of excitons in GaInNAs/GaNAs quantum wells

Abstract

Exciton photoluminescence (PL) in a GaInNAs/GaNAs quantum well was measured in the temperature range from 15 K to 300 K. Two striking features of the PL were observed: the nonmonotoneous temperature dependence of the Stokes shift and the abrupt increase of the PL linewidth in a rather narrow temperature range. These features are known to be strong indications of the hopping relaxation of excitons via localized states distributed in space and energy. Computer simulations of the hopping relaxation of excitons were carried out. Comparison between the simulation results and the experimental data provides an important and reliable information on the energy shape of the density of states and also on the energy range, in which localized states for excitons are distributed.

Configuration dependence of band-gap narrowing and localization in diluteGaAs1−xBixalloys

“…Previously, smaller reductions in the GaAs band gap were achieved in dilute nitrides, where nitrogen was incorporated at the As sites [11][12][13][14][15][16] . In that case the E g reduction was understood as the hybridization (anticrossing) of unoccupied nitrogen s orbitals with the host conduction band 17,18 , giving localized states responsible for the conduction band tail detected experimentally.…”

Photoluminescence investigation of high quality GaAs1−xBix on GaAs

“…The abrupt increase in the FWHM with temperature is explained by the increase in exciton's mobility with temperature. 20 As temperature increases, the excitons become more mobile, thus recombining from ͑and producing PL with͒ a broader ͑nonequilibrium͒ energy distribution. The FWHM then drops when excitons come into thermal equilibrium.…”

Non‐radiative recombination of optical excitations in (GaIn)(NAs) quantum wells

“…where 0 is the characteristic energy scale, which is of the order 10 meV for (GaIn)(NAs) alloys [4,5]. Inhomogeneities in nitrogen composition mainly cause fluctuations of the conduction band edge, whereas the edge of the valence band remains practically unperturbed.…”

“…The prominent features of the temperature-induced quenching of the photoluminescence (PL) intensity in (GaIn)(NAs) quantum wells (QW's) are the relatively weak (non-exponential) temperature dependence at low temperatures (T 50 K), succeeded by a steep drop by several orders of magnitudes and subsequent saturation that occurs at higher temperatures (T 150 K) [1,2]. A phenomenological model of the PL in disordered semiconductors [3] has been successful in explaining such features as the red shift of the PL peak energy with increasing temperature and narrowing of the PL linewidth at low temperatures commonly observed in (GaIn)(NAs) heterostructures [4,5], however non-radiative processes were disregarded so far.…”