Novel Stacked Passivation Structure for AlGaN/GaN HEMTs on Silicon With High Johnson’s Figures of Merit

We present a high-performance AlGaN/GaN high electron mobility transistors (HEMTs) on silicon substrate with novel stacked passivation layer (HfO2/SiO2). The stacked passivation structure can effectively modulate the electric field and reduce the electric field peak on the gate side, thus improving the breakdown voltage of the device. The prepared device with a gate length of 450 nm has a unit current gain cutoff frequency (fT) of 31.5 GHz, a maximum oscillation frequency (fMAX) of 46.3 GHz, and a three-terminal OFF-state breakdown voltage (BVgd) of 140 V at the gate-drain distance of
$2.3~\mu \text{m}$
. The estimated Johnson’s figure of merit (J-FOM = BVgd
$\times \text{f}$
T) is 4.4 THz•V, which is three and five times higher than that of the device with single HfO2 passivation layer and single SiO2 passivation layer, respectively. Furthermore, a significant suppression of the current collapse (~5.7%) is observed due to the electric field redistribution near the drain region. The results show that the AlGaN/GaN HEMTs with stacked passivation layer proved to be a promising candidate for high-performance radio frequency (RF) power device applications.