In-Situ Scanning Tunneling Microscope Study of Formation Process of Ultrathin Si Layer by Molecular Beam Epitaxy on GaAs(001)-(2×4) Surface

Abstract

In order to understand and to optimize Si interface control layer (Si ICL)-based passivation, the initial formation process of ultrathin Si layer by molecular beam epitaxy (MBE) on GaAs(001)-(2×4) surface at 300°C is studied in-situ by ultrahigh-vacuum (UHV) scanning tunneling microscopy (STM). Si atoms are found to fill the sites at the missing-dimer trenches of the GaAs (2×4) surface initially. As atoms from the background are also found to fill the As sites at the missing-dimer rows when residual As atoms exist in the MBE chamber after the growth of the GaAs layer. By these trench-filling processes, a (2×1) structure is formed. On the (2×1) structure, a disordered (1×2) overlayer is formed by additional Si supply. Further Si deposition leads to the formation of (2×1) and (3×1) overlayers above the disordered (1×2) structure.