Morphology of Epitaxial Growth of GaAs by a Molecular Beam Method: The Observation of Surface Structures

Homoepitaxial growth of GaAs was studied in situ in an ultrahigh‐vacuum high‐energy electron diffraction (HEED) system. Two surface structures, $\mathrm{GaAs}{\text{(1̄1̄1̄)−(19)}}^{\text{1/2}}$ and $\mathrm{GaAs}\text{(1̄1̄1̄)−2}$ , were observed during growth. The transition from one surface structure to the other was found to be a function of the deposition rate and the substrate temperature, with the high‐temperature structure being the ${\text{(1̄1̄1̄)−(19)}}^{\text{1/2}}$ . The film growth morphology was studied by the carbon replication technique. Growth by a step mechanism was observed on a bromine‐methanol etched surface while three‐dimensional nuclei were observed on a polished or contaminated surface.