Vapor phase passivation of (100) germanium surfaces with HBr

Hydrobromic acid (HBr) vapor was used to remove native oxide from an undoped (100) germanium (Ge) wafer with n-type conductivity and to passivate its surface against reoxidation. The Ge surfaces, examined by x-ray photoelectron spectroscopy, were suspended above a 48% HBr solution for 1, 10, 20, 60 min, and 24 h. A steady decrease in oxide thickness was observed for up to 60 min of HBr exposure time. Beyond this time, little or no difference was observed, and the wafers maintained subnanometer levels of oxidation. The stability of the passivated surface was then measured with each treated sample exposed to ambient air for 19 h. The samples exposed to HBr for 60 min or less reoxidized when exposed to air, while the sample previously exposed to HBr for 24 h showed levels of oxidation similar to the freshly passivated wafer, thereby demonstrating HBr vapor-phase treatment as a simple method for passivating Ge.