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) Al₂O₃ gate insulator. A 10-nmm Al₂O₃ 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-Al₂O₃ 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-Al₂O₃ gate insulator.