Electrical transport mechanisms in three dimensional ensembles of silicon quantum dots

Abstract

In this review, we try to derive a comprehensive understanding of the transport mechanisms in three dimensional ensembles of Si quantum dots (QDs) that are embedded in an insulating matrix. This understanding is based on our systematic electrical measurements as a function of the density of Si nanocrystallites as well as on a critical examination of the available literature. We conclude that in ensembles of low density QDs, the conduction is controlled by quantum confinement and Coulomb blockade effects while in the high density regime, the system behaves as a simple disordered semiconductor. In between these extremes, the transport is determined by the clustering of the QDs. In view of the clustering, two types of transitions in the electrical and optical properties of the system are identified. In order to understand them, we introduce the concept of “touching.” The application of this concept enables us to suggest that the first transition is a local carrier deconfinement transition, at which the concentration of the non “touching” QDs reaches its maximum, and that the other transition is associated with the onset of percolation in a continuous disordered network of “touching” QDs. It is hoped that our conclusions for the entire possible density range will provide guidance for the discussion and understanding of the transport in ensembles of semiconductor QDs in general and in ensembles of Si and Ge QDs in particular.

(Invited) The Effects of Confinement and Coulomb Blockade on the Transport in Ensembles of Si Quantum Dots

“…As detailed previously (4,11), we have co-sputtered then Si/SiO 2 composites by utilizing two source materials (targets): high purity sintered Si pallets and pure fused quartz. The 3 mm wide and 1 µm thick films were deposited on elongated quartz subsrates that were 13 cm long and 1 cm wide, such that during the sputtering process one end of the substrate is adjacent to the Si target and the other to the fused quartz target.…”

“…The photoconductivity was determined by subtracting the current in the dark from the current under illumination. Below, we refer to this difference as the photocurrent (4,15). Current-voltage (I-V) characteristics under various voltage scan rates have been routinely measured on the samples under and without illumination (4,15).…”

Structural parameters effect on the electrical and electroluminescence properties of silicon nanocrystals/SiO2 superlattices

“…Besides, the insulator matrix material usually states a drawback for carrier conduction, especially in the case of silicon oxide, whose barrier height can be hardly overcome by carriers [12]. After the long-term study on the electrical properties of bulk matrix-embedded NCs [13][14][15], many recent works have focused on the carrier transport taking place through the quasi-dielectric NC SLs. In these systems, lateral transport studies (i.e.…”

Silicon quantum dots embedded in a SiO2matrix: From structural study to carrier transport properties

“…1), which are the two more relevant tunneling mechanisms in QDs inside dielectric matrices. [47][48][49] In fact, inelastic scattering has been shown to be unimportant for highly quantum confined systems, such as the ones studied in the present work. 50,51 T…”