The Schottky barrier characteristics of aluminum contacts to In0.05Ga0.95As/GaAs strain‐relieved material were investigated. Acidic and alkaline wet chemical etching experiments were performed to determine the importance of semiconductor surface preparation prior to the deposition of the contact metal. Acidic etch treatments utilizing HCl and HF resulted in a range of ideality factors significantly greater than 1 (1.90–2.91 for HCl, 1.35–2.46 for HF), variable reverse bias leakage currents (0.038–0.440 &mgr;A/cm2for HCl, 23.0–110 &mgr;A/cm2for HF), and a range of barrier heights (0.88–0.93 eV for HCl, 0.63–0.77 eV for HF). In addition, the HCl treated devices exhibit time‐dependentI‐Vbehavior with continuous measurements, as well as changes in characteristics with both annealing and room‐temperature storage. The 10 s NH4OH:H2O (1:1) alkaline etch surface preparation produced stable Schottky contacts with a 0.79 eV barrier height, a 1.15±0.02 ideality factor, and ≊10 &mgr;A/cm2leakage current at −1 V bias.