Luminescence decay in disordered low-dimensional semiconductors

Abstract

The luminescence decay of excitons in disordered low-dimensional semiconductors with quantum confinement is shown experimentally to be characterized by a nonexponential profile and an absence of spectral diffusion. We are able to describe this luminescence as a hopping-assisted recombination using the correlation function approach to nondispersive transport developed by H. Scher, M. F. Shlesinger, and J. T. Bendler [Phys. Today 41, 26 (1991)]. We suggest a simple derivation of analytical functions which accurately describe the anomalous luminescence decays of disordered II-VI superlattices and of porous silicon, and show that this model includes exponential and Kohlrausch [Pogg. Ann. Phys. 119, 352 (1863)] (stretched-exponential) relaxations as special cases.

Apparent stretched-exponential luminescence decay in crystalline solids

“…Chen et al [9] studied the decay of luminescence in porous silicon and in CdSe-ZnSe superlattice, and found that the stretched-exponential behavior…”

Photoelectron and Photosensitization Properties of Silicon Nanocrystal Ensembles

“…The difference in coefficients D and D* can be related to the presence of a quadrupole (or higher moments of) interaction of excitons or an exchange interaction in the case of a substantial overlapping of their wavefunctions. Obtained ordinary differential equation (21) N excitation level, which was repeatedly noted by many researchers (see, e.g., (Chen et al, 1992) N initial excitation level. As will be shown in the next section, such a calculation can be performed in terms of the proposed model.…”

“…Numerous attempts were made to explain the causes of the stretched exponent of PL relaxation in the systems given above. For example, the authors of (Chen et al, 1992;Kanemitsu, 1996) relate this character of luminescence drop to the presence of disordered regions in these objects, which can be caused by a shape distribution of nanocrystals or a variation in their spatial arrangement. These factors induce a scatter of the recombination energies and probabilities of electronhole pairs, which is likely to result in luminescence kinetics of type (1).…”

“…The values of τ and depend on the excitation wavelength , temperature (Pavesi & Ceschini, 1993), and intensity and some other parameters (Chen et al, 1992) and are τ = 5-50 s and = 0.5-0.7 for PS samples with porosity P=70%. Note that Eq.…”

“…Note that Eq. (1) describes the PL relaxation kinetics in both ensembles of interconnected nc-Si in porous silicon layers (Mihalcescu et al, 1996;Pavesi & Ceschini, 1993) and other solid-state nanostructures, such as closely spaced (1-2 nm) nc-Si in a SiO 2 matrix (nc-Si/SiO 2 ) (Germanenko et al, 2001;Kanemitsu, 1996), CdSeZnSe superlattices (Chen et al, 1992), InGaN layered structures (Pophristic et al, 1998), and nanoporous SiGe solid solutions (Lebib et al, 1999). Numerous attempts were made to explain the causes of the stretched exponent of PL relaxation in the systems given above.…”