Abstract: A wafer includes a buried substrate; a layer of silicon (100) disposed on the buried substrate and forming multiple U-shaped grooves, wherein each U-shaped groove comprises a bottom portion and silicon sidewalls (111) at an angle to the buried substrate; a buffer layer disposed within the multiple U-shaped grooves; and multiple gallium nitride (GaN)-based structures having vertical sidewalls disposed within and protruding above the multiple U-shaped grooves, the multiple GaN-based structures each including cubic gallium nitride (c-GaN) formed at merged growth fronts of hexagonal gallium nitride (h-GaN) that extend from the silicon sidewalls (111).

Abstract: A wafer includes a buried substrate; a first layer of silicon (100) disposed on the buried substrate that includes silicon sidewalls (111) at an angle to the buried substrate and that form a bottom of each of multiple U-shaped grooves; a second layer of patterned oxide disposed on the silicon (100) that provides vertical sidewalls of each U-shaped groove formed within the first and second layers; a third layer of a buffer covering the first layer and partially covering the second layer partway up the vertical sidewalls; and multiple gallium nitride (GaN)-based structures disposed within the multiple U-shaped grooves, the multiple GaN-based structures each including cubic gallium nitride (c-GaN) formed at merged growth fronts of hexagonal gallium nitride (h-GaN) that extend from the silicon sidewalls (111).