Built-in strain, electric field, and spin polarization effects

in wide bandgap semiconductor materials and nano-devices

 

Professor A. Kadri*

 

Laboratoire d’Etude des Matériaux Opto-électronique & Polymères (L. E. M. O. P.)

Department of Physics, University of Oran (Es-Senia), 31300 Oran, ALGERIA

 *kadri.lemop.uo@mail.com

Abstract

Advanced optoelectronics and electronics applications put increasing and stringent demands on new properties of new materials with new systems, and new devices.  First of all, it becomes highly desirable to shrink the size of the devices down to the nanoscale (10^-9m). This is made so not only in order to make the devices smaller, smarter, chipper…, but it is done in the purpose of enhancing the quantum nature of materials properties, and revealing a set of new and very rich phenomena, unreachable neither at micro nor at macro scales. These issues are actually addressed by the evolving field of nanotechnologies and constitute the first part of my talk.

The second part of my talk addresses issues related to the necessity of finding new concepts and/or new phenomena to built new devices. I will focus on 3 such lines of interest: 1. built-in strain; 2. built-in polarization which leads to internal electric field and finally; 3. spin polarization. In each case, I’ll give examples of works done by our teams at the LEMOP Laboratory at the University of Oran Es-Sénia.

Built-in strain results from the mismatch between different materials associated in hetero-structures. This kind of internal strain can be controlled at the nanoscale. As far as this strain does not exceed some critical value, it can modify very deeply the properties of hetero-structures and constituent materials as well.  Materials properties as electronic, mechanical, optical, magnetic, … can be fine tuned in this way in a wide range to fit some desirable value of interest.

The internal electric fields which build up in nanostructures arise from spontaneous and/or piezoelectric polarizations effects. Such internal electric fields do also modify very dramatically the physical properties of nanostructures. They also can be controlled and tuned in a fine way, so that it can be possible to obtain a desired effect. 

The control of spin polarization can be also achieved in nano-systems, because of the strong spin degeneracy lifting, as a result of both quantum and size effects. It can lead to very interesting phenomena, and more particularly, to the so-called ‘’spintronics’’ which is of fundamental and practical importance in many applications as in quantum computations and memories for future computers.

 

Key words: nanomaterials, nanodevices, low dimensional systems, built-in strain, built-in electric field, spin polarization, ab-initio, DFT (FP-LAPW), k.P-theory, III-V Nitrides, II-VI oxydes , Lasers, Quantum Well heterostructures

 

Références:

 

[1] K.Zitouni, A.Kadri, P.Lefebvre, B.Gil, Superlattices and Microstructures 39, 91-96, (2006).

 

[2] Benharrats, K.Zitouni, A.Kadri, B.Gil, Superlattices and Microstructures, 47, 592, (2010).

 

 [3] A. Djellal,  A. Kadri, B. Gil, T. Breta-gnon, K. Zitouni,

3rd International Symposium on Growth of III-Nitrides( ISGN3),  4-10 July 2010, Montpellier France

 

[4] A. Djellal,  A. Kadri, B. Gil, T. Bretagnon, K. Zitouni, accepted  in Physica Status Solidi  C,  2011 .