Low ohmic-contact resistance in AlGaN/GaN high electron mobility transistors with holes etching in ohmic region

Good Ti/Al/Ni/Au ohmic contacts were achieved in AlGaN/GaN high electron mobility transistors (HEMTs) by using holes etching in an ohmic region. The ohmic contact with a contact resistance of 0.1 Ωmm was obtained. Compared with other methods which could reduce the ohmic-contact resistance, this method has simple process steps, low cost and can obtain stable device characteristics. The output characteristics and transfer characteristics of devices were analysed. The HEMTs using this method show lower contact resistance, smaller knee voltage and larger saturation current than the conventional HEMTs.