Performance enhancement of normally-off Al2O3/AlN/GaN MOS-Channel-HEMTs with an ALD-grown AlN interfacial layer

In this work, the performance of GaN-based MOS-Channel-HEMTs (MOSC-HEMTs) are shown to be greatly improved by a thin ALD-grown AlN interfacial layer inserted between the amorphous Al
2
O
3
gate dielectric and GaN-channel. The single-crystalline AlN interfacial layer effectively blocks oxygen from the GaN surface and avoids the formation of detrimental Ga-O bonds. Frequency-dispersion in C-V characteristics has been effectively suppressed. The maximum drain current and field-effect mobility are boosted from 410 mA/mm and 98 cm
²
/V·s in a conventional Al
2
O
3
/GaN MOSC-HEMT to 660 mA/mm and 165 cm
²
/V·s in an Al
2
O
3
/AlN/GaN MOSC-HEMT, owing to improved interface quality. The devices also deliver a high ON/OFF current ratio of ∼10
¹⁰
, and significantly reduced dynamic on-resistance degradation.