EFFECT OF DOPANTS ON ARSENIC PRECIPITATION IN GAAS DEPOSITED AT LOW-TEMPERATURES

High resolution x-ray diffraction using synchrotron radiation was use to characterize GaAs grown by MBE at low temperatures (LT-GaAs). LT-Ga As grown at 225-degrees-C is nonstoichiometric and exhibits a 0.15% la ttice expansion along the growth direction. Annealing LT-GaAs results in arsenic clusters with a well-defined orientation relationship with the GaAs matrix and a relaxation of the LT-GaAs lattice. The arsenic p recipitation corresponds to a classical case of diffusion controlled n ucleation and growth followed by coarsening. While the rates of growth and coarsening in the n-doped and the p-doped samples are observed to be identical, the effects of the superlattice seem to accelerate the precipitation kinetics in the p-n superlattice sample. The enhanced co arsening in the p-n superlattice sample is consistent with a previousl y proposed model involving interaction between charged precipitate and arsenic defects.