Antimony and bismuth passivations of InP and characterizations of InP metal-insulator-semiconductor structures fabricated by plasma oxidation of Sb- and Bi-passivated InP

Abstract

The passivation effects of Sb and Bi on InP were investigated. Sb and Bi were vacuum-evaporated on the InP (100) substrates with their thicknesses being changed from 0 nm (not deposited) to about 10 nm and the Schottky current–density–voltage (J–V) characteristics were measured for evaluation of the extent of passivation. The J–V characteristics were substantially improved when the Sb and Bi layers with appropriate thicknesses (about 6 nm for Sb and 4 nm for Bi). The reverse leakage current density largely decreased (from about 10−2 A/cm2 for the native InP sample) to 4×10−5 and 10−7 A/cm2 for, respectively, the Sb(6 nm)/InP and Bi(4 nm)/InP samples. The Schottky barrier heights were as high as 0.59 and 0.75 eV for, respectively, the optimum Sb- and Bi-layer thicknesses, as compared with that (0.45 eV) for the native InP one, which suggested the partial removal of the strong Fermi level pinning at (EC-0.2) eV (EC: conduction band bottom). The J–V characteristics showed the ohmic behavior as the thicknesses of Sb and Bi were large (>8–10 nm). The secondary ion mass spectroscopic (SIMS) data suggested that the Au–Bi-alloy/Bi-terminated-InP structure was fabricated with the optimum Bi thickness, while the Au–Bi-alloy/metallic–Bi/InP structure was produced for the thicker Bi layers, leading to the ohmic behavior (or small Schottky barrier height) because of low work function of Bi. The case of Sb can similarly be considered. It was also shown by the x-ray photoelectron spectroscopic (XPS) data that Sb and Bi removed the native oxides of InP by their reductive natures. Finally, the Sb/InP and Al/Bi/InP structures were exposed to helicon-wave excited O2–Ar plasma to fabricate the Sb2O3/InP and Al2O3–Bi2O3/InP metal-insulator-semiconductor (MIS) structures, which showed relatively well capacitance-voltage (C-V) characteristics.