Surface studies during molecular beam epitaxy of gallium arsenide

Abstract

Molecular beam epitaxy (MBE) has emerged as a practical growth technique from surface studies of the interactions of thermal molecular beams with solid surfaces under UHV conditions. From this origin, a number of surface analytical techniques have been applied in situ to assure that the desired conditions have been reached before and are being maintained during the crystal growth. The incorporation into the growth apparatus of surface diagnostic techniques, such as Auger electron spectroscopy (AES), reflection high energy electron diffraction (RHEED), and secondary ion mass spectroscopy (SIMS), is contributing important details on fundamental processes, which lead to the growth of high-quality monocrystalline GaAs films by MBE. The formation of reconstructed surface structures on GaAs(100) as a function of growth parameters were observed during growth by RHEED. AES has been used, for example, to determine the relative Ga/As ratios for different reconstructed surface structures, to investigate the impurity contamination on substrate surfaces, and to study the surface segregation of Sn in MBE GaAs during doping. Finally, impurities incorporated during the growth of GaAs by MBE may be detected by SIMS immediately after growth and within the reaction chamber. The MBE technique has also enabled us to alter the surface composition in a well-defined and reproducible manner and has been used to prepare flat, well-ordered clean surfaces, which are essential for surface experiments. Experiments suitable in the MBE apparatus include low energy electron diffraction (LEED), low energy electron loss spectroscopy (LEELS), photoelectron spectroscopy (UPS and XPS), and Raman scattering.