Reflection high energy electron diffraction measurements of molecular beam epitaxially grown GaAs and InGaAs on GaAs(111)

Abstract

Reflection high energy electron diffraction (RHEED) measurements were performed during the molecular beam epitaxial (MBE) growth of GaAs and InGaAs on GaAs(111) A and (111) B surfaces. Under a fixed Ga flux the period of these intensity oscillations was observed to increase with increasing As 4 flux on the 2 × 2 reconstructed GaAs(111) B surfaces. Layer thickness measurements, using cross-sectional transmission electron micrographs of AlAs/GaAs superlattices, indicated that the real growth rate did not correspond to the measured period of the intensity oscillations. The results are explained in terms of a reduction in Ga incorporation and an enhancement of Ga surface diffusion as the arsenic coverage of the 2 × 2 reconstructed (111) B surfaces is increased. The reduced Ga incorporation, on GaAs(111) B, promotes the formation of facets, commonly observed as three-dimensional islands or hillocks, which rob a portion of the Ga flux. The MBE growth and relaxation of strained InGaAs layers on GaAs(111) B were also studied by RHEED intensity oscillations and in situ surface lattice constant measurements. It is shown that by tuning the MBE parameters, during the growth of GaAs buffers and InGaAs layers on GaAs(111) B, premature strain relaxation due to the formation of twin defects can be prevented. Unlike the growth of InGaAs on GaAs(100) no two-dimensional to three-dimensional transition was observed even at high strains.