Surface reconstructions of cubic gallium nitride (001) grown by radio frequency nitrogen plasma molecular beam epitaxy under gallium-rich conditions

摘要

Cubic GaN has been grown under gallium (Ga)-rich growth conditions using radio frequency nitrogen plasma molecular beam epitaxy on MgO(001) substrates. Reflection high energy electron diffraction patterns indicate the smoothness of the c-GaN surface and show 2X and even 8X periodicities after the growth at sample temperature T_s < 200℃ and 1 X 1 at higher temperatures. Scanning tunneling microscopy images reveal a sequence of variant surface reconstructions including c(4X 12), 4X7, c(4X 16), 4X9, c(4X20), and 4X11. These variant reconstructions correspond to slightly different Ga adatom coverages all less than 1 /4 ML, with 4X11 having the highest, and c(4 X 12) the lowest Ga coverage. The electronic properties of these six variant reconstructions are investigated, and they are found to have a metallic nature.