In-Situ Contactless Characterization of Microscopic and Macroscopic Properties of Si-doped MBE-Grown (2×4) GaAs Surfaces

Abstract

Correlation between macroscopic electronic properties of the molecular beam epitaxy (MBE)-grown Si-doped GaAs (001) (2×4) 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 (2×4) 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.