Electrical transport in semiconductor quantum wire and quantum dot systems

• Research unit: COST
• Project number: C99.0114

Key words (English)

Quantized conductance; electron gas; quantum wells; quantum wires; quantum dots; quantum resistance; carrier injection; light emitting diode

Research programs (English)

COST-Action P5 - Mesoscopic electronics

Short description (English)

See abstract

Further information (English)

Full name of research-institution/enterprise: EPF Lausanne Laboratoire de physique des nanostructures LPN EPFL SB IPEQ LPN, PH D3 425 (Bâtiment PH)

Partners and International Organizations (English)

A, B, CZ, DK, FIN, F, D, H, I, NL, PL, SK, E, S, CH, GB

Abstract (English)

Electrical transport in low-dimensional semiconductor systems such as quantum wells (QWs), quantum wires (QWRs) and quantum dots (QDs) shows novel effects due to lateral quantum confinement and reduced system dimensionality. We have studied several aspects of such electrical transport using GaAs/AlGaAs structures grown by organometallic chemical vapor deposition (OMCVD) on nonplanar substrates. Two dimensional (2D) electron gas structures realized using OMCVD-grown modulation doped GaAs/AlGaAs QWs showed electron mobility higher than 800,000 cm2/V.s at 4K, among the highest values achieved so far with this grown technique. 1D electron gas structures were prepared by growing GaAs/AlGaAs QWR heterostructures on V-grooved substrates. Quantized conductance in the 1D electron gas was observed by varying the 1D electron gas density using a gated structure fabricated by electron beam lithography. Deviations from the expected quantized conductance in ideal 1D systems was explained in terms of quantum contact resistance between the 2D contacts and the 1D electron gas. Serially connected QWRs were realized using a similar technique and were used to investigate the intersubband scattering in the conducting 1D electron gas. In another set of experiments, we investigated electron and hole transport in GaAs/AlGaAs QWR light emitting diodes (LEDs). The QWR LEDs were grown on substrates patterned with arrays of V-grooves. In these structures, the carriers are referentially injected from the bulk contacts p into the QWRs, as evidenced by the electroluminescence spectra that are completely dominated by the QWR emission lines. This preferential injection mechanism is made possible by self-ordered AlGaAs vertical QWs that grow connected to the QWRs, forming a path for both electrons and holes form the contacts to the wire. Finally, we have constructed QWR-QD coupled systems using OMCVD on substrates patterned with modulated V-groove structures and used low temperature optical spectroscopy to study their confined carrier states.

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C99.0114