6500-V E-mode Active-Passivation p-GaN Gate HEMT with Ultralow Dynamic RON

This work demonstrates the E-mode active-passivation p-GaN gate HEMTs (AP-HEMTs) on sapphire substrate with blocking capabilities up to 6500 V. The AP-HEMT features an active passivation (i.e. a thinned p-GaN layer) extending from the gate edge towards near the drain contact. The 2DEG under the p-GaN gate and the active passivation is fully depleted at zero gate bias, resulting in E-mode operation with a V th = 0.8 V at I D = 10 μA/mm. With a positive V GS of 3.5 V, the AP-HEMT with L GD = 77 μm presents an R ON of 38.2 Ω-mm, and R ON,SP of 33.62 mΩ·cm ² . In the OFF-state, the active passivation is depleted from the drain side towards the gate edge. For L GD = 77 μm, the AP-HEMT presents a high breakdown voltage of 6573 V, resulting in a FOM (BV ² /R ON ) of 1.29 GW/cm ² that approaches the SiC limit. In the AP-HEMT, the effect of surface charges is screened by the active passivation layer, resulting in ultralow dynamic R ON . For the AP-HEMT with L GD = 77 μm, the measured dynamic R ON /static R ON is 1.15 after a 10-ms 3000-V V DS-OFF stress (delay time = 150 μs) and 1.02 after a 3-s 4500-V V DS-OFF stress (delay time = 300 ms). The results demonstrate that the active passivation can extend the E-mode p-GaN gate HEMT technology to kV-level applications.