Microscopie de biréfringence et caractérisation de matériaux à grand gap / Birefringence microscopy and characterisation of wide bandgap materials

Orateur : Soutenance de thèse de Ti Mai Hoa Le (LMGP - Grenoble)

Abstract Wide band gap (WBG) semiconductor materials such as Silicon Carbide (SiC) and Diamond have outstanding material properties. Many applications can benefit from WBG semiconductors. In order to improve material quality as well as to increase the range of technological applications of the WBG semiconductor materials, it is necessary to decrease or minimize the number of extended defects. This research work deals with the assessment, modelling and development of analytical techniques based upon the use of optical microscopy. The thesis dedicated to the identification of structural defects in Silicon Carbide (SiC) and diamond materials. Extended defects in 6H-SiC wafer and diamond materials were characterized by birefringence microscopy. The measured birefringence patterns of individual dislocations modelled. In the case of SiC, a good agreement is obtained between theory and experiment, which led to the proper determination of the Burgers vector values and background residual stress. All observed dislocations were almost vertical dislocations with a mixed character. Sometimes, their orientation changes resulting in the observation of a faint birefringence pattern. We compared birefringence data with etch pits formed after KOH etching. Combining both techniques is a method to discriminate between pure screw dislocations and mixed or pure edge dislocations. Typical dislocations in single crystal CVD diamond were determined by birefringence measurement and quantitatively modelled. Although the simulated images only approximate the experimental ones, the individual dislocations are determined to be threading edge dislocations with a possible Burgers vector a/2(011) or a/2(110). Sometimes, the vertical dislocations can convert to a horizontal or slightly tilted line and then turn vertical again resulting in the observation of two separated birefringence patterns. The dislocation propagation from the HPHT substrate into the CVD layer has been investigated by simultaneously analysing the HPHT substrate and the CVD layer in the same sample region.
Contact : colette.lartigue@minatec.inpg.fr
Plus d’infos sur : http://www.lmgp.grenoble-inp.fr/le-laboratoire/soutenance-de-these-de-ti-mai-hoa-le-microscopie-de-birefringence-et-caracterisation-de-materiaux-a-grand-gap-577820.kjsp

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