4:00 PM - *EQ13.07.01
Exploring the Properties of GaN Epilayers on van der Waals Substrates—The Case of Graphene and Muscovite Mica
Ana Cros1,Saül Garcia-Orrit1,Núria Garro1,Oleksii Klymov1,María José Recio-Carretero1,Marion Gruart2,Remy Vermeersch2,Fabrice Donatini2,Catherine Bougerol2,Bruno Gayral2,Stéphanie Pouget2,Edith Bellet-Amalric2,Nicolas Mollard2,Hanako Okuno2,Jean-Luc Rouvière2,Nathaniel Feldberg2,Bruno Daudin2
Univ de Valencia1,Univ. Grenoble-Alpes2
Show Abstract
The quality of III-nitride epilayers depends strongly on the characteristics of the substrate. The reduction of the number of extended defects in lattice mismatched epitaxial GaN layers grown on the most used substrates, namely sapphire and silicon, requires complex growth strategies that, despite the continuous advances, result in higher costs of the final device. The mismatch in thermal expansion coefficients of III-nitride layers and, for instance, Si substrate, is an additional source of extended defects associated with a strong substrate/layer chemical bonding. This motivates the exploration of alternative substrates, including the renewed interest in van der Waals epitaxy, where epitaxial growth is achieved through weak dipolar interactions. Materials such as graphite, mica, MoS2 or GaSe, have layered structures bonded via weak van der Waals interaction and can be easily cleaved, presenting very flat surfaces and the absence of dangling bonds. When GaN is grown on them, these substrates allow a significant relaxation of the epilayer strain and facilitate, at the same time, layer detachment [1].
We study the case of GaN grown by molecular beam epitaxy on graphene and muscovite mica as possible van der Waals substrates, addressing epilayer morphology, crystallographic phase and orientation, surface potential and strain. We also study the changes experienced by the graphene substrate during growth: doping, strain and, under certain conditions, the intercalation of a self-limited bilayer of metal atoms below graphene [2, 3]. In the case of mica, we observe that part of the strain accumulated in the GaN layer during growth relaxes by the formation of three-dimensional structures in the shape of telephone cord buckles, straight blisters or by more complex arrangements. The characteristics of these structures are analyzed in relation to the compressive strain of the surrounding material, the achieved relaxation and layer adhesion [4].
[1] Kim, J., Bayram, C., Park, H., Cheng, C. W., Dimitrakopoulos, C., Ott, J. A., Reuter, K. B., Bedell, S. W., & Sadana, D. K. (2014). Principle of direct van der Waals epitaxy of single-crystalline films on epitaxial graphene. Nature Communications, 5, 1–7. https://doi.org/10.1038/ncomms5836
[2] Gruart, M., Feldberg, N., Gayral, B., Bougerol, C., Pouget, S., Bellet-Amalric, E., Garro, N., Cros, A., Okuno, H., & Daudin, B. (2020). Impact of kinetics on the growth of GaN on graphene by plasma-assisted molecular beam epitaxy. Nanotechnology, 31(11), 115602. https://doi.org/10.1088/1361-6528/ab5c15
[3] Feldberg, N., Klymov, O., Garro, N., Cros, A., Mollard, N., Okuno, H., Gruart, M., & Daudin, B. (2019). Spontaneous intercalation of Ga and In bilayers during plasma-assisted molecular beam epitaxy growth of GaN on graphene on SiC. Nanotechnology, 30(37), 375602. https://doi.org/10.1088/1361-6528/ab261f
[4] Daudin, B., Donatini, F., Bougerol, C., Gayral, B., Bellet-Amalric, E., Vermeersch, R., Feldberg, N., Rouvière, J.-L., Recio Carretero, M. J., Garro, N., Garcia-Orrit, S., & Cros, A. (2021). Growth of zinc-blende GaN on muscovite mica by molecular beam epitaxy. Nanotechnology, 32(2). https://doi.org/10.1088/1361-6528/abb6a5