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Résumé

Des lasers tout cristal photonique émettant par la facette fabriqués dans le système (In)GaAs/AlGaAs et fonctionnant en régime de pompage optique sont démontrés. Nous montrons qu'une émission laser stable basée sur un point de fonctionnement de type DFB du second ordre peut être obtenue en utilisant des guides de type W3 (3 rangées de trous manquant). Nous démontrons la faisabilité d'une ingénierie de la longueur d'onde démission obtenue soit par modification du pas du cristal photonique (accord grossier), soit par déformation affine du cristal (accord fin). Nous étudions la sensibilité des cavités étudiées face aux conditions de pompage, à la longueur de cavité, et nous analysons la possibilité d'utiliser des guides plus larges.

Mots-Clés / Keywords

Abstract

The thermal oxidation of an Al-rich AlGaAs buried layer is a common established technique used to improve the performances of some optoelectronic devices, like VCSEL or optical waveguides, in terms of electro-optical confinement. This oxidation technique is usually proceeding laterally, which allows achieving good results but leads to some difficulties on the control of the shape and size of the oxidized areas. In this work, a new technology to oxidize GaAs/AlAs epitaxial structures which avoids these limitations is presented. This method consists of an oxidation through the top of the sample, allowing in consequence a total control of the shape of oxidation by means of photolithography. For this purpose the method has two steps: first, the intentional creation of defects in the top GaAs layer, in order to make it possible the oxidant species diffusion through this material, and second the planar oxidation of the AlAs layer. In this paper this technique is thoroughly studied: different methods to create defects in the GaAs layer have been analysed, and the optimization of the procedure has been achieved leading to a uniform oxidation and a reduced lateral oxidation spreading. Finally a comparison between the experiments and simulations has been realized in order to provide an explanation for this type of vertical oxidation. This innovating technique allows addressing separately the electrical and optical operating aspects of optoelectronic devices, thus opens to novel structures with controlled transverse optical behaviour.

Mots-Clés / Keywords

Résumé

Nous présentons ici l'étude de la faisabilité d'une nouvelle terminaison de jonction utilisant une tranchée profonde de 70 um de large et de 100 um de profondeur remplie par un matériau diélectrique. Les simulations, avec Sentaurus TCAD, ont montré une tenue en tension supérieure à 1200 V pour cette terminaison. Le remplissage de la tranchée de terminaison par un diélectrique étant indispensable, nous avons donc étudié la possibilité d'utiliser un polyimide à faible constante diélectrique. Outre ses bonnes caractéristiques électriques, le BenzoCycloButene (BCB) a permis un bon remplissage des tranchées profondes. Enfin, nous avons étudié le polissage du BCB par la technique de polissage mécano-chimique (CMP) dans le but d'aplanir et éventuellement de supprimer l'excès de BCB sur la surface de la plaque. En utilisant une suspension de polissage d'un pH 2,5 (acide), nous avons obtenu une vitesse de gravure par polissage d'environ 0,24 um/min pour le BCB. L'état de surface du BCB après CMP présente une rugosité, Ra, de 1,04 nm mesurée par AFM.

Abstract

In this work, a new design of high voltage (1200 Volts range) power SuperJunction MOSFET (SJMOSFET) is presented: the Deep Trench SJMOSFET (DT-SJMOSFET). Besides, a new junction termination, consisting in a 70 um width and 100 um depth trench filled by a dielectric, is proposed. Simulation results show that this junction termination exhibits the same blocking voltage capability as the base cell (central cell). In addition, the termination breakdown voltage dependence on the dielectric critical electric field (ECd) and its permittivity (¿rd) is studied. Finally, the possibility of filling the trench termination using low dielectric polyimide such as BenzoCycloButene (BCB) is successfully approved and the Chemical Mechanical Polishing of BCB is also discussed. These experimental results represent the key steps for a future complete fabrication process of DT-SJMOSFET.

Abstract

We report an experimental study of GaAs etching by ICP-RIE based on Cl2:N2 chemistry. The influence of the RF source power, the chlorine dilution, the RF platen power, and the process pressure at several substrate temperatures are investigated. An optimized process is proposed to get routinely GaAs nanowires of 1 ¼m high and about 30 nm in diameter with a full top-down approach combining electron beam lithography and Ni lift-off steps.

Mots-Clés / Keywords

Abstract

The thermal oxidation of an Al-rich AlGaAs buried layer is a common established technique used to improve the performances of some optoelectronic devices, like VCSEL or optical waveguides, in terms of electro-optical confinement. This oxidation technique is usually proceeding laterally, which allows achieving good results but leads to some difficulties on the control of the shape and size of the oxidized areas. In this work, a new technology to oxidize GaAs/AlAs epitaxial structures which avoids these limitations is presented. This method consists of an oxidation through the top of the sample, allowing in consequence a total control of the shape of oxidation by means of photolithography. For this purpose the method has two steps: first, the intentional creation of defects in the top GaAs layer, in order to make it possible the oxidant species diffusion through this material, and second the planar oxidation of the AlAs layer. In this paper this technique is thoroughly studied: different methods to create defects in the GaAs layer have been analysed, and the optimization of the procedure has been achieved leading to a uniform oxidation and a reduced lateral oxidation spreading. Finally a comparison between the experiments and simulations has been realized in order to provide an explanation for this type of vertical oxidation. This innovating technique allows addressing separately the electrical and optical operating aspects of optoelectronic devices, thus opens to novel structures with controlled transverse optical behaviour.

Mots-Clés / Keywords