The effective control of Pd/GaAs interface by sulfidation and thermal hydrogenation

A new technique using sulfidation and subsequent thermal hydrogenation is reported to minimize defective interracial bonds of Pd/GaAs Schottky contact, ultimately improving the electrical properties. Sulfur-passivation of GaAs surface prior to Pd metallization was very effective to exclude interracial compounds such as Ga oxides and As oxides, and resulted in both the reduction of reverse leakage current and the enhancement of barrier height. However, a defective interfacial bond of excess As inevitably appeared during Schottky metallization. The interface was annealed under vacuum and H₂ ambient at various temperatures from 100°C to 500°C, respectively. Pd/HCl-cleaned GaAs degraded its Schottky contact property after anneal at 400°C, while Pd/S-passivated GaAs maintained its property after anneal up to 400°C. Unlike to the vacuum annealed contact system, thermally-hydrogenated one showed a further improvement of electrical property. With nondestructive interface analysis using X-ray photoelectron spectroscopy, the hydrogenated Pd/GaAs interface turned to be free of defective bond, metallization-induced excess As. During the thermal hydrogenation of Pd/GaAs Schottky contact, the interracial excess As effectively sublimated by forming volatile As-hydrides through the reaction with hydrogen, and the interfacial hydrogenation at relatively low temperature could be expounded with a catalytic role of Pd metal.