Abstract
The spin-orbit interaction is a relativistic effect that couples the electron's displacement to its spin. This coupling is of great interest in solid state physics. Indeed, this coupling allows the propagation of information via the electron spin and not only via its charge, as it is the case in traditional microelectronics. This new approach, more than a simple improvement of the performances, is thus a change of the basic support of the information. Many practical applications have been envisaged. The mastery of spin-orbit coupling would allow the development of new spin-electronic systems (hence the word 'spintronics'), responding to the challenges of reducing energy consumption, for example. In the longer term, the control of the electronic spin would also allow the coding of information via a superposition of states, which would open the way to the realization of quantum bits (by analogy to the binary bit of a "classical" computer) realized in condensed matter.From this interest in spin-orbit coupling has emerged in recent years the subject of two-dimensional topological insulators, or spin quantum Hall effect insulators. These remarkable insulators are realized from materials with strong spin-orbit coupling.The first realizations of such insulators were obtained with semiconductors of the II-VI family. These insulators only survive at very low temperatures, of the order of Kelvin, because of particularities of the II-VI band structure. This motivated our search for new candidate materials for the observation of the spin quantum Hall effect at higher temperatures. During my thesis, I was interested in InAs/GaSb based structures, because in addition to the theoretical predictions and first demonstrations of the validity of these structures for the observation of the spin quantum Hall effect, the growth and fabrication of devices based on these III-V semiconductors is more widespread than for II-VI.In the first chapter, we present a review of recent work around topological insulators, from the emergence of this topic with graphene to the beginning of this work. We also develop the theoretical concepts at the basis of the experiments presented in this thesis.In chapter 2, we develop the experimental details and present the different InAs/GaSb based growths studied. We also detail the fabrication processes of the devices made from these same growths.Chapter 3 is dedicated to the magneto-transport measurements for the different devices. We demonstrate the validity of the theoretical calculations of band structure showing a clear increase of the gap size for the InAs/GaSb based structures, as well as the existence of an edge conduction whose properties are compatible with the topological character expected for these structures.