REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION MEASUREMENTS OF MOLECULAR-BEAM EPITAXIALLY GROWN GAAS AND INGAAS ON GAAS(111)

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 p eriod of these intensity oscillations was observed to increase with in creasing As4 flux on the 2 x 2 reconstructed GaAs(111)B surfaces. Laye r 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 oscil lations. The results are explained in terms of a reduction in Ga incor poration and an enhancement of Ga surface diffusion as the arsenic cov erage of the 2 x 2 reconstructed (111) B surfaces is increased. The re duced Ga incorporation, on GaAs(111) B, promotes the formation of face ts, commonly observed as three-dimensional islands or hillocks, which rob a portion of the Ga flux. The MBE growth and relaxation of straine d InGaAs layers on GaAs(111) B were also studied by RHEED intensity os cillations and in situ surface lattice constant measurements. It is sh own that by tuning the MBE parameters, during the growth of GaAs buffe rs and InGaAs layers on GaAs(111) B, premature strain relaxation due t o the formation of twin defects can be prevented. Unlike the growth of InGaAs on GaAs(100) no two-dimensional to three-dimensional transitio n was observed even at high strains.