SURFACE RECONSTRUCTION OF GAAS (001) DURING OMCVD GROWTH

Surface reconstruction of GaAs (001) during organometallic chemical vapour deposition (OMCVD) growth has been investigated with reflectance-difference spectroscopy (RDS). RD spectra reveal that surface reconstructions similar or identical to (4 x 2), (2 x 4), and c(4 x 4) that occur on surface prepared by molecular beam epitaxy (MBE) in ultrahigh vacuum (UHV) occur even in atmospheric pressure OMCVD growth environments. Based on the RDS database we established on static surfaces in UHV, we studied the structure of surfaces under both static and dynamic conditions in non-UHV ambients. We find, in contrast to previous models, that the surfaces under various non-UHV conditions exhibit dimer formation. In addition, OMCVD growth and atomic layer epitaxy (ALE) typically occur under disordered c(4 x 4)[d(4 x 4)]-like conditions where the surface is terminated by multilayers of As. When trimethylgallium (TMG) and arsine (AsH3) are supplied simultaneously, the surface structure varies as a function of the supply rates of TMG and AsH3, and the substrate temperature.