X-ray diffraction analysis of the structure of antisite arsenic point defects in low-temperature-grown GaAs layer

A method for the structure analysis of point defects in a semiconductor layer is developed by combining x-ray diffraction and growth of a superlattice where the concentration of point defects is periodically varied in the growth direction. Intensities of satellite reflections from the superlattice depend predominantly on the atomic structure of point defects, and hence this method can be applicable to the case of a low concentration of point defects. By using this method, the atomic structure of antisite As point defects in GaAs layers grown by molecular-beam epitaxy at low temperatures has been analyzed. Measured intensity ratios of the first-order satellite reflection in the lower angle side to that in the higher angle side for a number of (hkl) reflections are compared with those calculated based on structure models. The analysis has shown that experimental intensity ratios cannot be reproduced by models which include only a uniform tetragonal lattice distortion and local atomic displacements around an antisite As atom. A fairly good agreement between measured and calculated intensity ratios is obtained with a model which account for both gradual change in the tetragonal lattice distortion in the (0 0 1) plane and displacements of neighboring atoms away from the antisite As atom.