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.