Improved Electrical Characteristics of Al 2O 3/InP Structure by Combination of Sulfur Passivation and Forming Gas Annealing

The capacitance-voltage (C–V) characteristics of a Al2O3/InP capacitor fabricated by helicon-wave excited O2–Ar plasma oxidation of vacuum–evaporated Al were significantly improved by a combination of sulfur passivation of the InP substrate in (NH4)2Sx (for 60 min) and post-thermal annealing in forming gas (FG) containing 5% H2 (at 350°C) of the grown films after plasma oxidation. X-ray photoelectron spectroscopic (XPS) data indicated the formation of In–S bonds and suppression of InP oxidation after the sulfur passivation. The reason for the improved C–V characteristics is briefly discussed as being due to the termination of the incomplete or dangling bonds by sulfur and hydrogen.