Influence of lattice mismatch and growth rate on the decay of RHEED oscillation in the case of InGaAs/GaAs growth

The intensity decay of the oscillation of the reflection high-energy electron diffraction pattern's specular beam is analysed
during the molecular beam epitaxy of strained InGaAs/GaAs
heteroepitaxial structures. The oscillations' amplitude was
found to decrease exponentially with time during the InGaAs
growth. Further, the decay time constant decreases with InAs
mole fraction, indicating that the lattice strain increases
islanding during growth. A simple semi-quantitative model based
on the growth front roughening is formulated to explain the
results. Assuming that the oscillation decay is related partly
to the strain and partly due to kinetic effects during growth,
a decay component that is solely due to strain can be
separated; we find that the onset of increased roughening due
to the misfit strain component roughly corresponds to the
equilibrium critical layer thickness for misfit dislocation
generation.