Noise in Tunneling through a Quantum Dot Array

The shot noise suppression in a sample containing a layer of self-assembled InAs quantum dots has been investigated experimentally and theoretically. The observation of a non-monotonic dependence of the Fano factor on the bias voltage in a regime where only few quantum dot ground states contribute to the tunneling current is analyzed by a master equation model. Under the assumption of tunneling through states without Coulomb interaction this behaviour can be qualitatively reproduced by an analytical expression. Introduction Shot noise measurements provide a sensitive tool for probing transport properties of charged particles in mesoscopic systems, e.g. tunneling through semiconductor het-erostructures, which are not available by conductance measurements alone. The dynamic correlations between individual tunneling events can reveal details of the potential shape and the effects of electron-electron interaction [1]. Up to frequencies f of the inverse transit time of carriers the spectral power density of the current noise is frequency-independent: S(f) ≈ S(0). For an uncorrelated flow of electrons (Poisson statistics of individual tunnel-ing events) this value is proportional to the elementary charge e and the stationary current I: SP (0) = 2eI [2]. A reduction of this value refers to negative correlations in the current (sub-Poissonian noise), e.g. caused by the Pauli exclusion principle or repulsive Coulomb interactions, quantified by the Fano factor α = S(0)/SP ≤ 1. In double-barrier resonant tunneling structures this value is given by the ratio of the tunneling rates Γ E/C of emit-ter/collector barrier respectively: α = (Γ