Principal Investigator Jeehwan Kim
Van der Waals epitaxy (vdWE) has gained great interest for crystalline growth as it substantially relaxes the strict lattice matching requirements in conventional heteroepitaxy and allows for facile layer release from the vdW surface. In recent studies, vdWE was investigated on two-dimensional (2D) materials grown or transferred on arbitrary substrates, with the primary notion that the 2D material is the sole epitaxial seed layer in vdWE. However, the underlying substrate may still play a role in determining the orientation of the overlayers since the weak vdW potential field from 2D materials may barely screen the stronger potential field from the substrates.
Here, we reveal that the epitaxial registry of adatoms during epitaxy can be assigned by the underlying substrate remotely through 2D materials by modulating the interaction gap between the substrate and the epilayer. This study shows that remote epitaxial growth can be performed through a single-atom-thick gap defined by monolayer graphene at the substrate-epilayer interface. Simulations using density functional theory (DFT) prove that remote epitaxy can occur within a ~9 Å substrate-epilayer gap. We experimentally demonstrate successful remote homoepitaxy of GaAs(001) on GaAs(001) substrates through monolayer graphene. The concept is extended for remote epitaxy of other semiconductors such as InP and GaP. The grown single-crystalline films are then rapidly released from the vdW surface of graphene. To prove the functionality of GaAs film grown via remote homoepitaxy, we have successfully grown and fabricated light emitting diodes (LEDs) on graphene/GaAs substrate. This concept, here termed 2D material based layer transfer (2DLT), suggests a method to copy/paste any type of semiconductors films from the underlying substrates through 2D materials then rapidly released and transferred to the substrates of interest. With the potential to reuse graphene-coated substrates, 2DLT will greatly advance non-Si electronics and photonics by displacing the high cost of non-Si substrates.