Search for: [Abstrakt = "The effects of HCl\-based chemical and Ar\+ sputter etching treatment on \(100\) GaAs surface properties with the aim to develop the procedure of surface preparation before metal deposition have been investigated. Variable angle spectroscopic ellipsometry, X\-ray photoelectron spectroscopy, atomic force microscopy and photoluminescence have been used to study the surface characterization. We show that combining chemical etching in 5% HCl with Ar\+ sputter etching gives the best results for surface cleaning prior to metal deposition. The application of this two\-step treatment allows to obtain Ni\/AuGe\/Ni\/Au ohmic contact with rc = 2×10–6 Ωcm2 with excellent adhesion and long\-term thermal stability."]