Optimization of Ohmic Contact Metallization Process for AlGaN/GaN High Electron Mobility Transistor

In this paper, a manufacturing process was developed for fabricating high-quality AlGaN/GaN high electron mobilitytransistors (HEMTs) on silicon carbide (SiC) substrates. Various conditions and processing methods regarding theohmic contact and pre-metal-deposition BCl3 etching processes were evaluated in terms of the device performance.In order to obtain a good ohmic contact performance, we tested a Ti/Al/Ta/Au ohmic contact metallization schemeunder different rapid thermal annealing (RTA) temperature and time. A BCl3-based reactive-ion etching (RIE)method was performed before the ohmic metallization, since this approach was shown to produce a better ohmiccontact compared to the as-fabricated HEMTs. A HEMT with a 0.5 μm gate length was fabricated using this novelmanufacturing process, which exhibits a maximum drain current density of 720 mA/mm and a peak transconductanceof 235 mS/mm. The X-band output power density was 6.4 W/mm with a 53% power added efficiency (PAE).