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HL: Halbleiterphysik
HL 6: Quantum dots and wires: Transport properties I
HL 6.4: Talk
Monday, March 27, 2006, 11:00–11:15, BEY 118
Enhanced Shot Noise in Tunneling through coupled InAs Quantum Dots — •P. Barthold1, N. Maire1, F. Hohls1,2, R. J. Haug1, and K. Pierz3 — 1Institut für Festkörperphysik, Universität Hannover, Appelstraße 2, 30167 Hannover — 2Cavendish Laboratory, University of Cambridge Madingley Road, Cambridge CB3 0HE, UK — 3Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig
We investigate the noise properties of
vertically coupled
self-assembled InAs quantum dots (QDs) and find a surprising
enhancement of shot noise.
The two layers of InAs QDs are surrounded by AlAs tunneling
barriers. GaAs acts as a 3-dimensional emitter and collector.
Depending on the external bias voltage we find peaks in the
I/V-characteristic that correspond to electron transport through a
stack of two
vertically coupled QDs.
We find enhanced shot noise at these peaks. For the noise
measurements we focus on one peak in the I/V-characteristic. The
so-called Fano factor α is introduced to compare the
measured shot noise S with the full-Poissonian noise
Sfull=2eI that is expected for a single tunneling barrier:
α:= S/2eI. At both sides of the peak the Fano
factor α rises to values of α=1.4, while the noise
is reduced on the top of the peak (α<1). The Fano
factor α shows a significant temperature dependence while
the peak in the I/V-characteristic changes only slightly. We
discuss the different coupling mechanisms which can lead to such
an enhanced shot noise.