Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 64: Quantum Wires: Transport

HL 64.7: Vortrag

Mittwoch, 16. März 2011, 18:15–18:30, POT 251

Anomalous structures in the conductance of Si/SiGe quantum wires — •Joeren von Pock¹, Daniel Salloch¹, Gang Qiao¹, Ulrich Kunze¹, and Thomas Hackbarth² — ¹Lehrstuhl für Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum, D-44780 Bochum — ²DaimlerChrysler Forschungszentrum Ulm, D-89081 Ulm

We observe an anomaly in the differential conductance below the first plateau at G₀=4e²/h in Si/SiGe quantum wires (QWRs), in contrast to [1]. This anomaly is investigated in its magnetic (B ≤ 15 T) and thermal behaviour (20 mK ≤ T ≤ 4200 mK). The QWRs are fabricated from Si/SiGe heterostructures with an electron mobility of µ= 207,000 (125,000) cm²/Vs and a density of n_2D= 8.4· 10¹¹ (2.3· 10¹¹) cm⁻² at 1.5 K. The QWRs are constricted by an etch transfer in a low damage CF₄/O₂-Plasma, which causes a strong 1D-confinement potential. The anomalous conductance plateau is located near 0.6 G₀ at B = 0 T. As B increases parallel to the wire, the anomaly shifts down to 0.5 G₀, indicating Zeeman splitting. Our results are similar to the 0.7 anomaly in GaAs/AlGaAs quantum point contacts and QWRs [2]. Additional to the 0.7 anomaly a zero bias anomaly [3] is observed in transport spectroscopy at T = 22 mK. This anomaly is investigated as a function of magnetic field and temperature. At B > 1.5 T the anomaly splits into two peaks, and at T > 100 mK it does the same, which is untypical for GaAs/AlGaAs.
[1] S. Scappucci et al., Phys. Rev. B 74, 035321 (2006)
[2] K. J. Thomas et al., Phys. Rev. Lett. 77, 135 (1996)
[3] S. M. Cronenwett et al., Phys. Rev. Lett. 88, 226805 (2002)