Layer-by-layer growth of GaAs(0 0 1) studied by in situ synchrotron X-ray diffraction

We investigate the time-dependent surface evolution during molecular beam epitaxy of GaAs(0 0 1) using synchrotron X-ray diffraction at a newly-built dedicated beamline at the synchrotron BESSY II. The crystal truncation rods analyzed at growth temperature agree with the room-temperature β(2×4) reconstruction published in the literature. The layer coverage evolution during growth is analyzed by fitting the oscillating intensity along crystal truncation rods. Our results show that the structure of the reconstructed surface unit cell does not change during growth. Using numerical simulations, we determine the terrace size distribution on the surface at growth temperature and verify the validity of our analysis for multi-level initial surfaces, as long as the mean terrace size is larger than the nucleation distance during growth.