Electrical Transport Phenomena in Systems of Semiconductor Quantum Dots

Abstract

While a fairly good understanding of optical and transport properties that are associated with single quantum dots has emerged in recent years the understanding of the relation between these properties and the observed macroscopic optical and electrical properties of solid ensembles of such dots is still at a very rudimentary level. This is in particular so in regard to the transport properties where the interplay between inter-dot conduction and the connectivity of the dots network determines the macroscopic observations. Reviewing the basic concepts and issues associated with these two essential ingredients, and considering some recent experimental observations on quantum dot ensembles of CdSe and Si, an effort is made here to derive a whole-but-simple physical basis for the understanding of the transport and the optoelectronic properties of solid state ensemble of semiconductor quantum dots.

Electrical Transport Mechanisms in Ensembles of Silicon Nanocystallites

“…Also, we do not discuss here the ensembles of Si NCs that are embedded in the Si matrix of porous silicon. The transport mechanism in these systems that has been considered previously [3,5,[23][24][25] is quite different from that of Si NCs embedded in an insulating matrix since the Si matrix in porous silicon provides current routes that are parallel to those controlled solely by the Si NCs. In addition, in view of the limited scope of this chapter, we will not provide here an extended review of the theories and previous experimental results, but we will refer to those that we found essential for this chapter.…”

“…If the capacitance of the individual particle in its corresponding environment is C 0 , the energy needed to be supplied for the above electron-hole transfer by tunneling is then [5,7,8,11] …”

“…The interest in the last systems, however, is expected to follow the new basic physics that it reveals and the potential applications of such systems. Following the reasonable (though still controversial [6]) understanding of granular metals [7,8], where the electrical conduction takes place via metallic particles, additional significant insights into the transport mechanism [5,9] and new phenomena are expected in Si NCs due to the presence of confined levels [10]. In particular, the combination of Coulomb blockade (CB) effects and the quantum confinement (QC) restrictions can yield various resonant tunneling effects [11] as well as various quantum phase transformations [12] that are beyond the scope of this chapter.…”

“…There is even much less understanding of the transport mechanism in ensembles of 3D systems of Si NCs as there have been no comprehensive studies of the transport mechanisms in them [5]. In this chapter, we present probably the first comprehensive report of the transport mechanisms in ensembles of Si NCs embedded in insulating continuous matrices, adding (to the very common studies of the temperature dependence of the transport properties that is commonly applied for the determination of transport mechanisms) the very important parameter of the density of the NCs, N, the role of which has been overlooked in previous studies.…”

“…

While the optical [1][2][3] properties of various ensembles of individual Si nanocrystallites (NCs) and the memory-charge storage (CS) characteristics of two-dimensional (2D) arrays of Si NCs [4] have been investigated by many researchers, relatively little attention was paid to the transport properties of 3D ensembles of such quantum dots (QDs) [5]. The interest in the last systems, however, is expected to follow the new basic physics that it reveals and the potential applications of such systems.

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