Berlin 2005 – scientific programme
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HL: Halbleiterphysik
HL 58: Poster IIb
HL 58.3: Poster
Tuesday, March 8, 2005, 16:30–19:00, Poster TU F
Noise measurements of vertical coupled InAs quantum dots — •P. Barthold1, N. Maire1, F. Hohls1, A. Nauen2, R. J. Haug1, K. Pierz3, and T. Bryllert2 — 1Institut für Festkörperphysik, Universität Hannover, D-30167 Hannover — 2Div. of Solid State Physics, P.O. BOX 118, SE-221 00 Lund — 3Physikalisch- Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig
We present noise measurements of resonant single electron tunnelling through individual and vertical coupled self-organised InAs quantum dots (QDs) at temperatures down to 1.5 K.
In the first case our samples consist of a GaAs/AlAs/GaAs tunnelling structure with self-organised InAs QDs embedded in the AlAs. Depending on the bias voltage we find that the shot noise is suppressed in respect to the full Poissonian value 2eI. This suppression is characterised by the Fano factor α = S / 2eI whose modulation was perceived in the experiment. We investigate the noise generated by the sample with a current amplifier in a range from 0 to 10 kHz, and a spectrum analyser that uses Fast Fourier Transformation. Above 1 kHz the noise shows a frequency-independent behaviour indicating the presence of shot noise.
In the second case we investigate with the same setup two different types of samples, GaInAs/InP/GaInAs and GaAs/AlAs/GaAs heterostructures in which two layers of vertical coupled InAs QDs are embedded. With both samples we observe definite peaks in the I-V-characteristic as aspected. Due to the bias voltage modulations of α are found. While the peaks in the I-V-characteristic show a slight change at different temperatures the modulation of α shows a distinct behaviour.