Enhancement of breakdown voltage in AlGaN/GaN HEMT using passivation technique for microwave application

The AlGaN/GaN High Electron Mobility Transistor (HEMT) on Silicon Carbide (SiC) substrate with SiO2 passivation is proposed in this paper. The maximum drain current of 0.8 A/mm is observed at Vgs = 0 V for gate width (WG) = 600 μm. The breakdown voltage of device with SiO2 passivation is compared with breakdown voltage of device with SiN passivation and it is found that the breakdown voltage improved in the device with SiO2 passivation. The breakdown voltage of the device with SiO2 and SiN passivation are 312 V and 287 V, respectively. Furthermore, the improvement in the breakdown voltage is observed with increase of buffer thickness. The obtained breakdown voltages are 312 V, 390 V and 412 V for buffer thickness of 2 μm, 3 μm and 5 μm, respectively. In addition to breakdown analysis, the impact of passivation on intrinsic capacitance is investigated and found that the device with SiO2 passivation exhibits a reduction in gate-source capacitance (CSG) and gate - to - drain capacitance (CGD).