Nucleation and surface roughness in self-limiting monolayer epitaxy of GaAs

The surface morphology produced by molecular layer epitaxy (MLE) was invest igated using atomic force microscopy (AFM), The surface morphology and roug hness estimated quantitatively were not consistent with the temperature dep endence of self-limiting growth. The degree of roughness had two states in the monolayer growth temperature range from 445 to 534 degreesC. In the gro wth temperature region over 475 degreesC, nucleated islands along [1 (1) ov er bar0] the direction one monolayer high were observed on the grown surfac e. When the growth temperature was less than 475 degreesC, such nucleation did not occur and a smooth surface without islands was obtained with a roug hness of less than one monolayer. To understand island formation, the nucle ation and the islands at each growth cycle were investigated.