Sb and Bi passivation effects on GaAs

Passivation effects of Sb and Bi on GaAs were investigated. Sb and Bi were vacuum-evaporated on GaAs (100) substrates. The Au/Sb/GaAs and Au/Bi/GaAs Schottky diode samples showed improved current-density-voltage (J-V) characteristics, in which the reverse leakage currents substantially decreased and the Schottky barrier heights increased, when the Sb-and bi-layer thicknesses were appropriate (∼ 6 nm for Sb and ∼ 8 nm for Bi). X-ray photoelectron spectroscopic (XPS) and secondary ion mass spectroscopic (SIMS) data, together with the J-V characteristics, indicated that the passivation effects stem from the probable surface termination of GaAs with Sb and Bi, the removal of the native oxides of GaAs due to the reductive natures of Sb and Bi, and suppression of Au diffusion into GaAs by these layers. The GaN/GaAs structure was fabricated by the plasma nitridation of the Sb/GaAs sample in the helicon-wave excited N₂ plasma.