Ge-spacer technology in AlGaN/GaN HEMTs for mm-wave applications

GaN-based high electron mobility transistors (HEMTs) are the most promising option for power amplification at frequencies above 30 GHz. However, the difficult technology of nitride devices has hindered the aggressive scaling of these transistors needed for high frequency applications. Also, the need of a relatively thick passivation layer to avoid current collapse in these transistors has significantly limited the high frequency performance of the devices. In this paper, we introduces an advanced technology which uses a Ge sacrificial layer to fabricate passivated AlGaN/GaN HEMTs with gate lengths down to 90 nm, while maintaining a high breakdown voltage and minimum parasitic capacitances. Using these devices, we demonstrate record high frequency performance at both small and large signal levels