M. Pristovsek et al., Dynamic study of the surfaces of (001) gallium arsenide in metal-organic vapor-phase epitaxy during arsenic desorption, J APPL PHYS, 87(3), 2000, pp. 1245-1250
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].