Multiple trapping on a comb structure as a model of electron transport in disordered nanostructured semiconductors
- PDF / 337,285 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 39 Downloads / 181 Views
ONIC PROPERTIES OF SOLID
Multiple Trapping on a Comb Structure as a Model of Electron Transport in Disordered Nanostructured Semiconductors R. T. Sibatov* and E. V. Morozova** Ulyanovsk State University, ul. L’va Tolstogo 42, Ulyanovsk, 432017 Russia * email: [email protected] ** email: kat[email protected] Received June 2, 2014
Abstract—A model of dispersive transport in disordered nanostructured semiconductors has been proposed taking into account the percolation structure of a sample and joint action of several mechanisms. Topological and energy disorders have been simultaneously taken into account within the multiple trapping model on a comb structure modeling the percolation character of trajectories. The joint action of several mechanisms has been described within random walks with a mixture of waiting time distributions. Integral transport equations with fractional derivatives have been obtained for an arbitrary density of localized states. The kinetics of the transient current has been calculated within the proposed new model in order to analyze timeofflight exper iments for nanostructured semiconductors. DOI: 10.1134/S106377611504024X
1. INTRODUCTION The problem of electron transport in nanostruc tured materials is important both theoretically and technologically [1, 2]. In most cases, these materials are disordered structures where the kinetics of charge carriers (electrons, holes, and ions) is often anomalous and cannot be described within the standard diffusion approach [3–14]. Dispersive transport is a remarkable example of such kinetics. This type of nonGaussian transport is observed in many disordered materials dis tinguishing in microscopic structure: in amorphous semiconductors, porous solids, polycrystalline films, liquidcrystal materials, polymers, etc. [6, 9, 14]. Dispersive transport is explained by various mech anisms: multiple trapping of carriers into localized states distributed in the mobility gap, phononassisted hopping, percolation over conducting states, etc. (for more details, see [3, 6, 14]). The necessity of allow ance for the morphology of a nanostructured, in par ticular, nanoporous material remains topical when describing electron transport, e.g., in dyesensitized solar cells [1, 2]. The possibility of the joint action of several transport mechanisms should also be taken into account. We emphasize that the existing analyti cal approaches to the description of dispersive trans port (Scher–Montroll, Arkhipov–Rudenko, Rose– Fowler–Weisberg, and Nikitenko models) disregard both the percolation character of trajectories, which is due to the topological disorder, and joint action of sev eral mechanisms.
In this work, the joint effect of topological and energy disorders on transientcurrent curves is con sidered within the multiple trapping model on energydistributed localized states in a comb struc ture modeling the percolation character of trajecto ries in a nanostructured material. The joint action of several mechanisms is studied within the random walk model w
Data Loading...
