Effect of growth conditions on stoichiometry in MBE-grown GaAs

The effects of varying As4/Ga flux ratio r, substrate temperature and growth rate on the deviation from stoichiometry in GaAs grown by MBE have been investigated. The deviation from stoichiometry was directly measured by detecting intensity variation of a weak quasiforbidden (200) reflection of x rays. Using this new method, we obtained the following results: in the regions of r<1.0 and r>2.0, higher densities were detected in the As lattice plane. The behavior for r<1.0 is contrary to the expectation of decrease of As. A possible explanation for this higher reflection in r<1.0 is that some Ga atoms may exist at interstitial site in the As lattice plane. It is also seen that densities of atoms in the As lattice plane decrease with increasing substrate temperature. In correspondence with the results that the growth condition with flux ratio r=1.4 minimizes the deviation from stoichiometry, it is found that GaAs films grown under the condition r=1.4 show the highest quality of the electrical and optical properties.