Recombination dynamics in dry-etched (Cd,Zn)Se/ZnSe nanostructures: Influence of exciton localization

Abstract

The influence of exciton localization on the recombination dynamics in dry etched ͑Cd,Zn͒Se/ZnSe wires and dots has been studied using time-resolved photoluminescence spectroscopy. The observed size and temperature dependence of the excitonic lifetime can be explained quantitatively taking into account the interplay between nonradiative carrier loss at the sidewalls and trapping of free excitons into localized states. From the data, a density of localized states N L ϭ7ϫ10 8 cm Ϫ2 and an average localization energy E A ϭ2.8 meV can be deduced. ͓S0163-1829͑99͒13703-2͔

Effects of reabsorption and spatial trap distributions on the radiative quantum efficiencies of ZnO

“…36 If exciton trapping were occurring, then the spectrum would redshift as a function of time: at very early times, the PL would primarily correspond to free excitons that have not yet become trapped. After a delay characterized by the exciton localization time, the PL would primarily correspond to trapped excitons which, by definition, would emit photons of lower energy upon annihilation.…”

On Brauer's theorem and Cassini's ovals

“…In the samples with d(InP) = 20, 10 and 5 nm the measured PL transients are mono-exponential, which is not the case in the sample with d(InP) = 3 nm. A two-exponential decay can account for the experimental PL transients in this sample, which can be associated to a recombination dynamics of a population formed by both near-free and localized excitons in a given proportion [29,30]. However, given that all the samples of series A have been grown under similar conditions, and the InP spacer thickness being the main difference between them, carrier (exciton) transfer (tunnelling) towards other wires in every of the six InAs layers is possible, because of the strong vertical delocalization of the carrier wavefunction for such a narrow spacer, as will be shown below.…”

Optical Characterization of ZnSe-Based Quantum Structures Fabricated by CH4/H2 Reactive Ion Etching

“…Even though the dry etching technique such as reactive ion etching (RIE) has an advantage of anisotropic nature, there is the serious problem that it causes damage not only at the etched surface but also inside the materials. However, concerning details about RIE-induced damage for II-VI compounds, it has not yet been clarified, because studies have been concentrated on structures patterned on single quantum well (SQW) samples [5,6,8,9]. In the SQW, fluctuations both in well width and in composition complicate to reveal genuine effects.…”

“…Direct fabricating technique to realize a low-dimensional system such as quantum wires and quantum dots is electron beam lithography followed by an etching process. In addition to the wet etching technique [1][2][3][4], dry etching technique [5][6][7] has been employed to transfer nanoscale wire patterns to II-VI compound semiconductors. Even though the dry etching technique such as reactive ion etching (RIE) has an advantage of anisotropic nature, there is the serious problem that it causes damage not only at the etched surface but also inside the materials.…”

“…Accordingly, we believe that the main contribution to the RIE-induced damage comes from lattice defects which may act as centers of DAP transitions and exciton binding states. It has been suggested that an optical inactive surface layer, which leads to the nonradiative recombination of excited carriers and short lifetime of luminescence, is formed after RIE [1,5,6]. On the other hand, the ion-induced damage seems to extend much deeper in the materials [9,11].…”