Ultra high vacuum scanning tunneling microscope observation of vicinal (001) GaAs surface and (117)B GaAs surface grown by metalorganic vapor phase epitaxy

We have observed the atomic arrangement on vicinal (001) GaAs surfaces and (117)B GaAs surface grown by metalorganic vapor phase epitaxy using an ultra high vacuum scanning tunneling microscope without exposure to air. Multilayer step regions and atomically flat terrace regions are alternately observed to the misorientation direction for both (001) GaAs surfaces misoriented by 2° toward [110] direction (called A-surface) and [110] direction (called B-surface). At the terrace region, c(4 × 4) reconstruction units are dominant. For B-surface, (4 × 2) and (4 × 3) like reconstruction units were observed between each monolayer step at multilayer step region, which correspond to (119)B GaAs surface. For A-surface, the reconstruction units are not clear at multilayer step region, but step-step separation is about 1.4 nm, which is close to (117)A GaAs surface. For (117)B GaAs surface, a lot of monolayer steps and (4 × 3) and (5 × 3) like reconstruction units were observed with significant undulations for whole area, which suggests that (117)B GaAs surface grown by MOVPE is thermodynamically unstable.