Density of States and Conductivity of Granular Metal or Array of Quantum Dots

Abstract

The conductivity of a granular metal or an array of quantum dots usually has the temperature dependence associated with variable range hopping within the soft Coulomb gap of density of states. This is difficult to explain because neutral dots have a hard charging gap at the Fermi level. We show that uncontrolled or intentional doping of the insulator around dots by donors leads to random charging of dots and finite bare density of states at the Fermi level. Then Coulomb interactions between electrons of distant dots results in the a soft Coulomb gap. We show that in a sparse array of dots the bare density of states oscillates as a function of concentration of donors and causes periodic changes in the temperature dependence of conductivity. In a dense array of dots the bare density of states is totally smeared if there are several donors per dot in the insulator.

13 pages, 15 figures. Some misprints are fixed. Some figures are dropped. Some small changes are given to improve the organization

References in corpus (5)

• Coulomb effects in granular materials at not very low temperatures
• Variable-range hopping in quasi-one-dimensional electron crystals
• Single-Electron Charging and Coulomb Interaction in InAs Self-Assembled Quantum Dot Arrays
• Electron transport in two-dimensional arrays
• Coulomb blockade and quantum tunnelling in the low-conductivity phase of granular metals

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• Compact chromium oxide thin film resistors for use in nanoscale quantum circuits
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