Interface-controlled Au/GaAs Schottky contact with surface sulfidation and interfacial hydrogenation

We report a GaAs passivation method using sulfidation and hydrogenation to achieve the Au/GaAs interface free of defective interfacial compounds, through which improves the electrical properties of the Schottky contact. A sulfur-passivated GaAs Schottky diode exhibited improved contact properties, for example an enhanced barrier height and the lower reverse leakage current compared to the diode with conventional HCl-cleaned GaAs. The combination of the H-plasma treatment and the predeposition of an ultrathin Au overlayer enable to control the defective interfacial state of metallization-induced excess As: the Au overlayer seems to effectively protect GaAs from plasma-induced damage and attenuate the energy of penetrating hydrogen then the hydrogenated interface became defect-free since interfacial excess As effectively sublimated as volatile As hydrides. The reverse leakage current was reduced by an order and photoluminescence efficiency was greatly enhanced while there was no change in the dopant profile of GaAs substrate and none of Si-H. We describe a mechanism of the evolution of interfacial bonds during the processes to correlate to the improved electrical properties, which are systematically characterized by the surface/interface analysis tools such as x-ray photoelectron spectroscopy and attenuated-total-reflection Fourier-transform infrared spectroscopy and particularly the role of excess As is discussed in detail.