Improved fabrication process for obtaining high power density AlGaN/GaN HEMTs

An improved process for fabricating high power density AlGaN/GaN HEMTs is now presented. Previously, a silicon nitride passivation layer has been shown to improve the power performance of AlGaN/GaN HEMTs by minimizing surface related dispersion effects. Typically, this passivation layer has been deposited during the final stages of the fabrication process, with the device active area exposed to various potentially harmful plasmas and chemical treatments. In the new process, a high quality silicon nitride layer is deposited early in the fabrication process, serving to both protect the AlGaN surface from damage and to minimize dispersion related phenomena. In addition, the silicon nitride layer provides an opportunity for forming well defined field-plated gate structures. 0.6 /spl mu/m /spl times/ 150 /spl mu/m gate devices built with this process have demonstrated state-of-the-art CW output power and power added efficiency of >15.6 W/mm and 44% respectively at 10 GHz, when operated at 60 V drain voltage.