In-situ contactless characterization of microscopic and macroscopic properties of Si-doped MBE-grown (2x4) GaAs surfaces

Correlation between macroscopic electronic properties of the molecular beam epitaxy (MBE)-grown Si-doped GaAs (001) (2 x 4) surfaces with microscopic atomic structures was in situ investigated using ultrahigh vacuum scanning tunneling microscope (UHV STM), UHV contactless capacitance-voltage (C-V), UHV photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) techniques. Surface defects including kinks, steps, holes, islands and missing As atoms in As dimer rows were observed at the Si-doped (2 x 4) GaAs surfaces. Contactless C-V results directly showed the surface Fermi level pinning. The observed macroscopic C-V and PL behavior cannot be explained by the previous kink-acceptor model, assuming that each kink forms a discrete acceptor level, but it indicates Fermi level pinning by U-shaped continuous surface states.