Dynamic study of the surfaces of (001) gallium arsenide in metal-organic vapor-phase epitaxy during arsenic desorption

We have investigated by reflectance anisotropy spectroscopy the arsenic des orption from GaAs (001) at various temperatures in metal-organic vapor-phas e epitaxy to obtain reaction orders and activation energies. The highest ar senic coverage, found at low temperatures with arsine stabilization, corres ponds to a (4 x 3) reconstruction. Without arsine, arsenic starts to desorb and less arsenic-rich reconstructions are observed, depending on temperatu re: c(4 x 4) (below 800 K), beta 2(2 x 4) (below 920 K), alpha(2 x 4), and only with hydrogen carrier gas finally (4 x 2) (above 950 K). Above 920 K t he reaction order differs in hydrogen and nitrogen atmosphere, probably due to an etching effect of hydrogen radicals. The five different desorption p rocesses show either a first- or zero-order time dependence. First order is related to the desorption from the terraces and zero order to desorption f rom the steps (or kinks) on the surfaces. The activation energies for all p rocesses are around 2.5 eV. This energy is, therefore, assumed to be the ac tivation energy for the removal of an arsenic dimer from the surface. (C) 2 000 American Institute of Physics. [S0021-8979(00)09203-3].