By performing time-resolved optical non-degenerate pump-probe experiments, we study the relaxation dynamics of spin-polarized excitons in wurtzite epitaxial GaN and in nitride nanostructures. Those materials are indeed promising candidates for spintronic applications because of their weak spin-orbit coupling and large exciton binding energy (~ 17 meV and ~ 26meV in bulk GaN, respectively).
In epilayers, we show that the high density of dislocations increases dramatically the spin relaxation of electrons and holes through the defect assisted Elliott-Yafet mechanism. That makes the exciton dephasing time very short.
In high quality GaN/AlGaN quantum wells, both the exciton-spin lifetime S and the exciton dephasing-time T2 were determined via pump-probe spectroscopy using polarized laser pulses and time-resolved four wave-mixing experiments. The evolution of both quantities with temperature shows that spin relaxation occurs in the motional narrowing regime up to 80 K. Above this threshold, the thermal energy becomes large enough for excitons to escape from the QW. Such measurements demonstrate that GaN-based heterostructures can reach a very high degree of control that was previously mostly restricted to conventional III-V semiconductors and more specifically to the arsenide family.
Mathieu Gallart, Marc Ziegler, Bernd H. Hönerlage, Pierre Gilliot, Eric Feltin, Jean-François Carlin, Raphaël Butté, and Nicolas Grandjean, "Spin and phase relaxation dynamics in GaN and GaN/AlGaN quantum wells (Presentation Recording)," Proc. SPIE 9551, Spintronics VIII, 95510S (Presented at SPIE Nanoscience + Engineering: August 09, 2015; Published: 5 October 2015); https://doi.org/10.1117/12.2190575.4519370530001.
Conference Presentations are recordings of oral presentations given at SPIE conferences and published as part of the proceedings. They include the speaker's narration with video of the slides and animations. Most include full-text papers. Interactive, searchable transcripts and closed captioning are now available for most presentations.
Search our growing collection of more than 29,500 conference presentations, including many plenaries and keynotes.