Low-resistance ohmic contacts to high-electron-mobility transistors (HEMTs) are essential to ensure optimal device performance. Besides low contact resistance (< 1 Omega mm), good surface morphology and edge acuity are also desirable. We report a systematic study of the ohmic contact scheme Ti/Al/Ti/Au, where the total film thickness was kept constant at 285 nm and the relative ratios of Ti/Al inner layer thicknesses were varied. While the film with the highest Ti/Al ratio had slightly inferior electrical properties, the layer smoothness and edge acuity were far superior to the other ohmic contact schemes. (c) 2006 The Electrochemical Society.