High Temperature AlGaN/GaN MISHEMT With W/AlON Gate Stack and Imax>1 A/mm at 500 ∘C

This work demonstrates a scaled (L ${}_{\text {g}}=50$ nm, L ${}_{\text {gs}}=270$ nm, L ${}_{\text {gd}}=360$ nm) RF AlGaN/GaN MISHEMT with a record current density of 1.16 A/mm at 500°C and a corresponding Ion/Ioff of 9. The device was made using a plasma enhanced atomic layer deposited (PEALD) aluminum oxynitride (AlON) gate dielectric and passivation which was found to increase the 2D electron gas density by 33%. The devices were fabricated utilizing a sputtered tungsten refractory metal T-gate process and achieved a room temperature ft/fmax of 28.5/28.8 GHz, limited by RF loss through the conductive silicon substrate. Overall, the promising results highlight the potential of RF GaN HEMTs to operate at high temperatures to enable new applications.