Structural transformations in low-temperature grown GaAs : Sb

Sb-doped and Sb-free GaAs films were grown by molecular beam epitaxy (MBE) at low temperature (LT) and were annealed in the MBE set-up at various temp eratures within the range of 500-900 degreesC. The concentrations of arseni c antisites in as-grown samples obtained using near-infra-red optical absor ption were found to be as high as 6 x 10(19) and 7 x 10(19) cm(-3) in Sb-do ped and Sb-free samples, respectively. Samples were studied by high-resolut ion x-ray diffractometry (HRXRD) and transmission electron microscopy (TEM) . Despite the high concentration of intrinsic point defects, x-ray rocking curves demonstrated perfect crystalline quality in as-grown samples. After annealing at temperatures of 500-700 degreesC, the lattice mismatch decreas ed in both Sb-doped and Sb-free samples, but in Sb-doped samples the reduct ion was much higher than would be expected for the antisite defect concentr ation determined from optical measurements. The segregation of isovalent Sb impurity into the As clusters was suggested. Upon annealing at temperature s higher than 700 degreesC, Sb-doped samples manifested a strong broadening of the diffraction maximum related to the LT GaAs:Sb layer. The TEM and HR XRD studies revealed that high-temperature annealing resulted in formation of dislocation loops attached to the large As clusters.