Routine measurement of the absolute As4 flux in a molecular beam epitaxy system with conventional RHEED equipment

TheGa/As flux ratio during epitaxial growth of GaAs is a very important parameter for the quality of the deposit. A low As4 flux leads to formation of nonstoichiometric films with a rough surface structure. On the other hand, excessive As4 flux is the reason for incorporation of As at Ga-sites (antisite defects). In addition, a high As population reduces the Ga surface migration and increases the surface roughness. In this work, a method was shown for an accurate measurement of the actual As4 flux during molecular beam epitaxy (MBE) growth of GaAs using the sharp cut-off of the RHEED oscillations at flux ratiosJ/GaJAs4 higher than 1.53. In order to calculate the absolute As4 flux, the ratio of incorporated Ga-atoms per As-atom was determined from the decreasing growth rate under the condition of As deficiency. The reproducability of the As4 flux measurements was found to be better than ±4% and the data were in good agreement with quadrupole mass spectroscopy measurements of the As4 flux.