Enhanced precipitation of excess As on antimony delta layers in low-temperature-grown GaAs

Delta doping with antimony isovalent impurity has been employed as a precur sor for two-dimensional precipitation of excess arsenic in GaAs grown by mo lecular-beam epitaxy at low substrate temperature (LT-GaAs), and subsequent ly annealed. LT-GaAs films delta doped with indium isovalent impurity showe d previously to provide two-dimensional As cluster sheets were studied for comparison. Small clusters observed by transmission electron microscopy at the Sb delta layers had an unusual lens shape and, probably, nonrhombohedra l microstructure. These clusters induced strong local strains in the surrou nding GaAs matrix. After annealing under the same conditions, the clusters at the Sb delta layers were found to be bigger than those at the In delta l ayers. Additionally, nucleation of the arsenic clusters at the Sb delta lay ers occurs at a relatively low annealing temperature. The observed precipit ation features indicate that delta doping with Sb is more effective for two -dimensional precipitation of the excess As in LT-GaAs as compared with In delta doping. (C) 1999 American Institute of Physics. [S0003-6951(99)02511- 5].