High RF performance improvement using surface passivation technique of AlGaN/GaN HEMTs at K-band application

Abstract

A surface passivation technique of high electron mobility transistor (HEMT) devices is reported. The passivated HEMT device has a much higher RF performance of FT and Fmax than a non-passivated one. The AlGaN/GaN HEMT has a short gate length of 0.15 μm using an E-beam lithography system and very low ohmic contact resistance of 1.3 × 10-6 Ωcm-2 using a rapid thermal processing alloy system. In addition, to protect the active layer from the surface trap, an SiO2 thin film passivation process is applied by the plasmaenhanced chemical vapour deposition system. The fabricated AlGaN/GaN HEMT exhibits a maximum drain current of 900 mA/mm and a maximum transconductance of 320 mS/mm. In particular, this device produces excellent RF performance of small-signal characteristics, such as a current gain cut-off frequency (fT) of 55 GHz and maximum oscillation frequencies (fmax) of 130 GHz. © The Institution of Engineering and Technology 2013.