Demonstration of 16 THz V Johnson's figure-of-merit and 36 THz V fmax.VBK in ultrathin barrier AlGaN/GaN HEMTs with slant-field-plate T-gates

In this work, ultrathin barrier (similar to 6nm) AlGaN/GaN high-electron-mobility transistors (HEMTs) with in situ SiN gate dielectric and slant-field plate (SFP) T-gates were fabricated and analyzed. Since the proposed scheme of gate dielectric and SFP effectively suppresses the gate leakage and alleviates the peak electric field (E-field) around gate region, the maximum breakdown voltage (V-BK) was improved to 92V, which is 54V higher than that of the conventional device. The fabricated ultrathin AlGaN/GaN HEMT with 60-nm SFP-T-gate exhibited the peak f(T) of 177GHz and peak f(max) of 393GHz, yielding high figure-of-merits of f(T).V-BK = 16THz V and f(max).V-BK = 36THz V. Moreover, load-pull measurements at 30GHz reveal that these devices deliver output power density (Pout) of 4.6W/mm at V-ds=20 V and high power-added efficiency up to 52.5% at V-ds=10 V. Essentially, the experimental results indicate that the employment of SFP and in situ SiN gate dielectric is an attractive approach to balance the breakdown and speed for millimeter wave devices. Published under an exclusive license by AIP Publishing.