Soutenance de thèse de Merwan Mokhtari

Investigation of processing-induced defects in GaAs based vertical cavity surface emitting lasers (VCSEL) with aluminum-oxide confinement layers

Abstract :

Nowadays, VCSELs are key components for datacom applications. The work presented is focused on the study of the mechanical deformations induced by the steps initiating the manufacturing process of GaAs based VCSELs operating at 850 nm and including aluminum-oxide as confinement layers. The use of non-destructive techniques such as the measurement of the degree of polarization of photoluminescence (DOP) and micro-photoluminescence allowed us to obtain a precise vision both spatially and quantitatively of these mechanical deformations. The effects induced in VCSEL structures after dielectric deposition used as a hard mask for etching, plasma etching of the P-mesa and wet thermal oxidation of the confinement layers have thus been characterized. Stress values ​​of several tens of MPa were measured in a VCSEL structure conducted through the various process steps up to oxidation. We have experimentally demonstrated that it is possible to reduce the mechanical stress generated by the oxidation process by up to 25% by performing a post-oxidation annealing. A study by STEM-EELS of the oxide morphology and its atomic composition at a local scale has helped us to refine the physical interpretation of the effect related to this annealing. Based on the experimental DOP results, analytical and numerical modeling approaches were also carried out to predict the mechanical deformations induced by the different process steps mentioned above. Finally, we presented the first electrical and optical characterizations performed on such VCSELs showing that the studied devices are in agreement with the internal specifications and that the fabrication process can be considered as uniform.

Jury :

Rapporteurs avant soutenance :
Isabelle SAGNESDirectrice de Recherche CNRS, C2N, Marcoussis
Guilhem ALMUNEAUDirecteur de Recherche CNRS, LAAS, Toulouse
Examinateurs :
Martina BAEUMLER Dr. rer. nat., Ingénieure de Recherche, IAF, Freiburg, Allemagne
Juan JIMENEZ Professeur, GdS Optronlab, Université de Valladolid, Espagne
Charles CORNET Maître de Conférences HDR, Institut FOTON, INSA de Rennes
Co-encadrants de thèse :
Christophe LEVALLOIS Maître de Conférences, Institut FOTON, INSA de Rennes
Philippe PAGNOD-ROSSIAUX Responsable Développement Wafer Process, 3SP Technologies SAS, Nozay
Directeur de thèse :
Jean-Pierre LANDESMAN Professeur, IPR, Université de Rennes 1
Invités :
François LARUELLE (co-directeur de thèse) Chief Technical Officer (CTO), 3SP Technologies SAS, Nozay
Daniel T. CASSIDYProfesseur émérite, Université de McMaster, Canada

Pot :

à l'IPR, cafétéria du Bat 11A (salle 116), à partir de 13h00.