MECHANISM OF MULTIATOMIC STEP FORMATION DURING METALORGANIC CHEMICAL-VAPOR-DEPOSITION GROWTH OF GAAS ON (001) VICINAL SURFACE STUDIED BY ATOMIC-FORCE MICROSCOPY

The detailed behavior and mechanism of multiatomic step formation proc esses during metalorganic chemical vapor deposition (MOCVD) of GaAs on vicinal surfaces are systematically investigated using an atomic forc e microscope (AFM). Under the low growth rate condition, the step flow growth mode with regular stripe is obtained, and the final terrace wi dth is almost independent of the substrate misorientation angle. The r esult suggests that the barrier height difference for surface migratin g Ga atoms between the terrace site and the step site is small, and th e final terrace width is mainly determined by a migration length. Thre e-dimensional nucleation and growth mode with irregular steps are also obtained under the high growth rate condition. However, as the AsH3 p artial pressure increases, irregular steps are no longer observed. For these results, we discuss the multiatomic step formation mechanism.