Recombination dynamics of localized excitons in a CdSe/ZnSe/ZnSxSe1

Abstract

Optical properties of localized excitons have been studied in a highly strained CdSe quantum well with 1-ML thickness by employing time-resolved photoluminescence ͑PL͒ and nonlinear PL spectroscopy under various excitation conditions. At 20 K, the time-integrated PL from the well layer was peaked at 2.7276 eV with a linewidth of 21 meV under low excitation intensity ͑0.11 J/cm 2). The lifetime ranged from 200 ps to 50 ps as the monitored photon energy was changed from the low-energy tail to the high-energy one. The behavior could be well understood as a result of exciton localization, which is induced by terraces and islands with units of ML thickness fluctuation lying at the interface between CdSe and ZnSe. An emission with the fast decay component was observed at the low-energy side of the peak ͑2.7168 eV͒ under higher excitation condition. The emission could be well resolved as a positive component by the nonlinear PL measurement, and originates from the many-body effect of localized excitons, which is probably attributed to localized biexcitons. ͓S0163-1829͑96͒07828-9͔

Excitons, biexcitons, and phonons in ultrathin CdSe/ZnSe quantum structures

“…To study the dynamics of exciton localization, most of the experiments [31][32][33] have used an excitation energy resonant to the band of delocalized excitons, and the subsequent luminescence decay was analyzed by rate equations of a multilevel system. Such an approach always results in a manyparameter model.…”

Role of localized excitons in the stimulated emission in ultra-thin CdSe/ZnSe/ZnSSe single quantum-well structures

“…The wavelength, the pulse width and the repetition rate were 390 nm, 1.7 ps and 82 MHz, respectively. Details of the TRPL system are given elsewhere [5].…”

“…Recently it has been found that the degree of exciton localization in CdSe/ZnSe QWs is much larger than that in ZnCdSe/ZnSe QWs with Cd concentration in the range of 20%, because well-width fluctuation in CdSe QWs lead to larger shifts of the confinement energy of carriers [4,5]. In this paper the mechanism of photo-pumped stimulated emission in CdSe single quantum wells (SQWs) with well-layer thickness (L W ) of 1, 2 and 3 monolayers (ML) is discussed.…”

CdSe Layers of Below Critical Thickness in ZnSe Matrix: Intrinsic Morphology and Defect Formation

“…By varying the molecular beam epitaxil (MBE) growth conditions and thickness of thin CdSe layer on a ZnSe surface, three different regimes have been reported: (i) Stranski-Krastanov (SK) island growth mode (above tcr) [4][5][6], including thermal activation regime [7], (ii) pseudomorphic growth of thin CdSe or ZnCdSe quantum-well-like (QW-like) layers (below t^,.) [8][9][10], and (iii) coexistence of extended islands and the alloy-like phase (w < 1 ML) [11][12][13]. The SK growth mode was found to produce the dot-like CdSe-based islands with lateral sizes far beyond 10 nm, which cannot provide sufficient 3D confinement.…”

“…The pseudomorphically grown CdSe/ZnSe heterostructures (w < 3 ML) are characterized by a decrease in a PL peak line width with the reduction of w, observed even in a sub-monolayer region, which contradicts an expectable line width increase for thin QWs due to potential fluctuation on interface roughness. Zhu et al [8] have interpreted this fact for sub-monolayer w region by the formation of uniform ZnCdSe alloy layer at the CdSe/ZnSe interface. The recent investigations have revealed the complicated structure of fractional monolayers (FMs) involving both the alloy-like homogeneous layer, which can probably be formed by small, with respect to rB, islands, and extended 2D ones [11][12][13].…”