Amelioration of the Interfacial Properties in Au/GaAs Schottky Contact Using Sulfidation and Hydrogenation

We report on a novel passivation method of GaAs with sulfidation and hydrogenation, fabricating Au/GaAs interface free of defective interfacial bonds and ultimately improving the electrical property of its Schottky contact. In this study, the realistic bonding features of GaAs surface/interface were directly monitored using high resolution X-ray photoelectron spectroscopy and the electrical properties were evaluated with current–voltage (I–V) method. Sulfur-passivation with (NH4)2S solution, as surface treatment of GaAs, was effective to make Au/GaAs interface completely free of GaAs oxides, while the presence of interfacial excess As originated from Au metallization was unavoidable. To control this defective As compound, we introduced hydrogen-plasma treatment after deposition Au film to S-passivated Schottky diode. The S-passivated and successive hydrogenated Au/GaAs interface showed only non-defective interfacial compound of Ga sulfide, free of any defective bonding state, since interfacial excess As seemed to effectively sublimate by forming volatile As hydride. With complete absence of interfacial excess As, the reverse leakage current of its Schottky diode was dramatically reduced about ten times, compared with only S-passivated sample. From capacitance–voltage (C–V) dopant profile, this two-step method was found to have no damage into GaAs substrate due to the barrier effect of pre-coated Au layer on GaAs surface.