Oxide-free InAs(111)A interface in metal-oxide-semiconductor structure with very low density of states prepared by anodic oxidation

Abstract

In this letter, we present structural, compositional, and electrical characteristics of anodic oxide layer-based metal-oxide-semiconductor (MOS) capacitors on n-type InAs(111)A, along with the effect of a thin fluorinated interfacial passivation layer. Electrochemical oxidation in acid electrolyte with addition of fluorine (NH4F) led to the formation of oxygen free well-ordered wide gap fluorinated interfacial layer at InAs(111)A with the fixed charge (Qfix) and density of interface states (Dit) in the range of (4–6) × 1010 cm−2 and (2–12) × 1010 eV−1 cm−2, respectively. We found that MOS capacitors showed excellent capacitance-voltage characteristics with very small frequency dispersion (<1% and <15 mV). Fluorinated interfacial layer consists of crystalline isostructural compound with the InAs substrate, which remains intact with the atomic smoothness and sharpness that explain unpinned behavior of the Fermi level.