High breakdown voltage AlGaN/GaN MOS-HEMTs-on-Si with atomic-layer-deposited Al2O3 gate insulator

We have proposed and fabricated AlGaN/GaN MOSHEMTs employing an atomic-layer-deposited (ALD) Al
₂
O
₃
gate insulator. A 10-nmm Al
₂
O
₃
served as passivation layer as well as gate dielectric, which results in stable blocking characteristics. The drain leakage current of the proposed device was decreased by five orders. The leakage current of the conventional device (MESFET) with L
_GD
of 15 μm was 87 μA/mm while that of the proposed device with the same L
_GD
was 0.2 nA/mm. The ratio of the gate leakage current to the total leakage (I
_G
/I
_DSS
) was decreased to 0.1 while that of the conventional one was over 0.8. It was found that ALD-Al
₂
O
₃
gate insulator made a significant contribution to the device blocking capability by suppressing gate leakage effectively. The measured breakdown voltage (V
_BR
) of the MOSHEMTs with L
_GD
of 20 μm was 1980 V while the V
_BR
of the conventional HEMTs device with the same L
_GD
was 1310 V. In addition, the MOS-HEMTs with 3-μm gate exhibited good dc and pulse characteristics due to passivation effect of the ALD-Al
₂
O
₃
gate insulator.