Lattice site locations of excess arsenic atoms in gallium arsenide grown by lowhyphen;temperature molecular beam epitaxy

摘要

The excess As atoms present in ashyphen;grown GaAs buffer layers grown by molecular beam epitaxy at low substrate temperature (sim;200thinsp;deg;C) was measured by particle induced xhyphen;ray emission to be sim;4times;1020atoms/cm3. The lattice site location of these excess As atoms in the layer was studied by ion channeling methods. Our results strongly suggested that the excess As atoms are located in an interstitial position close to the substitutional As atoms with a projected displacement sim;0.3 Aring; into the lang;110rang; channel. These results are consistent with the lang;111rang; split interstitials model suggested from TEM results. After annealing at 600thinsp;deg;C these excess As atoms coalesce forming As precipitates.