SURFACE RECONSTRUCTION OF GAAS (001) DURING OMCVD GROWTH

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