Van der Waals epitaxial growth of few layers WSe₂ on GaP(111)_B

Abstract 2D material epitaxy offers the promise of new 2D/2D and 2D/3D heterostructures with their own specific electronic and optical properties. In this work, we demonstrate the epitaxial growth of few layers WSe₂ on GaP(111)_B by molecular beam epitaxy. Using a combination of experimental techniques, we emphasize the role of the growth temperature and of a subsequent annealing of the grown layers under a selenium flux on the polytype formed and on its structural and morphological properties. We show that a low growth temperature promotes the formation of the 1T′ and 3R phases depending on the layer thickness whereas a higher growth temperature favours the stable 2H phase. The resulting layers exhibit clear epitaxial relationships with the GaP(111)_B substrate with an optimum grain disorientation and mean size of 1.1° and around 30 nm respectively for the 2H phase. Bilayer 2H WSe₂/GaP(111)_B heterostructures exhibit a staggered type II band alignment and p-doped character of the epi-layer on both p and n-type GaP substrates. This first realisation of stable p-type WSe₂ epi-layer on a large-area GaP(111)_B substrate paves the way to new 2D/3D heterostructures with great interests in nanoelectronic and optoelectronic applications, especially in the development of new 2D-material p-n junctions.