Nanostructured semiconductors

First-Principles investigations of intrinsic and Si-doped GaAs nanowires
(Nahid Ghaderi, Nadia Binggeli, and Maria Peressi)

High quality GaAs nanowires (NWs) are nowadays experimentally grown on different substrates, regularly shaped and nicely oriented. At variance with the bulk phase, they show a prevalence of wurzite structure with respect to zincblende and a p-type behavior with respect to the possible amphoteric behavior upon Si incorporation. Motivated by these recent experimental findings, we investigate by first principles pseudopotential calculations the structural stability of free-standing GaAs NWs, comparing zinc-blende and wurtzite structures for NWs of different size. We study also the relative stability and the effect on the electronic properties of substitutional Si impurities at different Ga and As sites in NWs with different diameter, aiming at identifying the most favoured configurations.

Nahid Ghaderi, Maria Peressi and Nadia Binggeli
Structural properties and energetics of intrinsic and Si-doped GaAs nanowires: First-principles pseudopotential calculations
Phys. Rev. B 81, 155311 (2010)

Nahid Ghaderi, Maria Peressi and Nadia Binggeli
First-Principles Investigations of Intrinsic and Si-doped GaAs Nanowires: Structural Stability and Electronic Properties
Frontiers of Fundamental and Computational Physics: 9th International Symposium", AIP Conference Proceedings 1018, Issue 1, 193 (2008)

In collaboration with:

• CNR-INFM TASC National Laboratory - MBE group (S. Rubini, F. Martelli, F. Jabeen, A. Franciosi)

Semiconductor heterostructures for spintronic applications
(N. Ghaderi, A. Debernardi, A. Baldereschi, M. Peressi)

Spin-polarized conduction carriers can be generated from a ferromagnetic source and injected into a non-ferromagnetic semiconductor channel. Half-metallic ferromagnets such as Co2MnSi and NiMnSb or other Heusler alloys are promising candidates for spintronic devices because of their good structural matching with traditional semiconductors and because they are completely spin-polarized at the Fermi level, being therefore efficient spin-polarized carriers sources. One of the main challenges in spin injection is that half-metallicity may be lost at the interface. We address this problem in different systems, with the aim of predicting those interface morphologies that can be favored under particular thermodynamic conditions and can maintain the peculiarity of full spin-polarization of carriers.

A. Debernardi, M. Peressi, and A. Baldereschi
Spin polarization and band alignments at NiMnSb/GaAs interfaces
Comp. Mat. Sci. 33 (1-3), 263-268 (2005)

N. Ghaderi, S. J. Hashemifar, H. Akbarzadeh, and M. Peressi
First principle study of Co2MnSi/GaAs(001) heterostructures
J. Appl. Phys. 102, 074306-(1-7) (2007)

M. Peressi, A. Baldereschi, and S. Baroni
Ab-initio studies of structural and electronic properties
in: Characterization of Semiconductor Heterostructures and Nanostructures
ISBN: 978-0-444-53099-8, editor: C. Lamberti (Elsevier, 2008), p. 17-54