In this paper, the influence of a recess etching process on the contact resistance and the relevant electrical properties of In 0.12 Al 0.8 Ga 0.08 N/AlN/ GaN HEMTs is presented. Without etching, the contact resistance is typically 0.9 Ω mm. By recess etching R cont is reduced to 0.2 Ω mm. A strong correlation of R cont to the maximum drain saturation current (I DSþ ) and to the maximum transconductance (G mMax ) is observed. Devices with R cont of 0.2 Ω mm show I DSþ of 1.7 A mm À1 and G mMax of 620 mS mm À1 , respectively.