Abdallah Ougazzaden

Professor

Georgia Institute of Technology/School of Electrical and Computer Engineering

International Research Laboratory IRL GT-CNRS, GT-Lorraine the European Campus of GIT

(Metz, France)

Quasi van der Waals (QvdW) epitaxy is a new approach for epitaxial growth of three dimensional (3D) materials on two-dimensional (2D) layered materials. This approach has seen fast progress in the last decade, attracting tremendous attention, especially for III nitrides, where new pathways have been opened for new optoelectronic/electronic nitride devices and their applications. QvdW offers huge advantages compared to the conventional 3D/3D epitaxy. The weak QvdW interactions between the III-Nitrides heterostructures and 2D layered materials is a major enabler because it allows strain due to large lattice and thermal mismatches to relax elastically without generation of additional dislocations and defects. In addition, with simple sticky holders (tapes, PDMS, metals…), the III-Nitrides heterostructures can be mechanically detached over a large area from its substrate and transferred as membranes to arbitrary carriers. The substrates can then be reused without any heavy Chemical-Mechanical-Polishing (CMP). For the 2D layered materials it was confirmed that hexagonal boron nitride (hBN) could be the material of choice for QvdW epitaxy of III-Nitrides heterostructures. It exhibits a good stability at high temperature, an excellent compatibility with III-nitrides growth conditions and growth systems (MOCVD, MBE, CVD…) and can be grown on different types of substrates. In this talk an overview of QvdW epitaxy will presented. The growth mechanism will be described. III-Nitride heterostructures such as LEDs, HEMTs, solar cells and detectors grown on hBN will be presented. Mechanical liftoff and transfer approaches will be compared in term of materials quality and crack generation after growth and post exfoliation. Device performance before and after transfer will be described. Finally, the perspectives and future applications of this approach will be discussed.