Strong photoluminescence and low surface state densities on clean and silicon deposited (001) surfaces of GaAs with (4 x 6) reconstruction

In an attempt to determine an optimum initial GaAs surface for application of the silicon interface control layer (Si ICL)-based surface passivation method, properties of the (4 x 6) reconstructed Ga-rich (001) surface of GaAs were investigated before and after Si deposition. An ultrahigh vacuum (UHV)-based multi-chamber system was used where samples were prepared by molecular beam epitaxy (MBE) and characterized by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), UHV photoluminescence (PL), and contactless capacitance-voltage (C-V) methods. For comparison, (2 x 4) and c(4 x 4) As-rich surfaces were also prepared. STM observation clarified the microscopic structure of the (4 x 6) surface. XPS measurements confirmed the Ga-rich nature of the initial surface and detected the reduction of band bending on both initial and Si-deposited (4 x 6) surfaces. A surprisingly large band-edge PL intensity was obtained on the (4 x 6) surface, and it further increased after Si deposition, reaching as high as 8.9 times that of the (2 x 4) surface. UHV contactless C-V measurements indicated low and wide N-ss distributions on the initial and Si-deposited (4 x 6) surfaces. All the results consistently indicate that the (4 x 6) surface is the most promising surface for application of the Si ICL-based surface passivation process for GaAs.