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 (f(T)) 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 m. The estimated Johnson's figure of merit (J-FOM = BV(gd)xfT) is 4.4 THz center dot 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 (similar to 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.

Automated summary

We propose a high-performance AlGaN/GaN high electron mobility transistor (HEMT) on a silicon substrate with a novel stacked passivation layer (HfO2/SiO2). The stacked structure effectively modulates the electric field, improving the device's breakdown voltage. The prepared device exhibits a unit current gain cutoff frequency (f(T)) 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 a gate-drain distance of 2.3 μm. In addition, the device demonstrates three and five times higher Johnson's figure of merit (J-FOM = BV(gd)xfT) compared to those with a single HfO2 passivation layer and a single SiO2 passivation layer, respectively. The AlGaN/GaN HEMTs with stacked passivation layer show promising potential for high-performance radio frequency (RF) power device applications.