Takuya Kokawa

High-power AlGaN/GaN MIS-HFETs with field-plates on Si substrates

In this paper, GaN-based MIS-HFET devices on 4-inch Si substrates were fabricated, and the device characteristics were examined. As a result, the breakdown voltage was improved to be over 2.45 kV using high-resistive carbon doped buffer layers with a larger thickness of over 7.3 µm. The maximum drain current was estimated to be over 115 A using MIS-structures. A trade-off between the specific on-resistance (RonA) and the breakdown voltage (Vb) was improved using carbon doped buffer layers, resulting in obtaining RonA = 5.9 mΩcm2 and Vb = 1730 V simultaneously with the gate-width of a 340 mm. Furthermore, the field-plate structure was introduced into MIS-HFET structures. We have examined the suppression of a current collapse phenomenon owing to the combination of the gate field-plate structure and a conductive Si substrate with MIS-HFET devices.

Over 1.7 kV normally-off GaN hybrid MOS-HFETs with a lower on-resistance on a Si substrate

In this study, normally-off GaN hybrid MOS-HFET devices on 4-inch Si substrates were fabricated, and the device characteristics were examined. As a result, the breakdown voltage (Vb) was improved using a combination of a high-resistive carbon-doped back barrier layer and a thin channel layer of 50 nm. The specific on-resistance (RonA) was estimated to be less than 7.1 mΩcm2 for Lgd = 12 μm, and Vb was estimated to be over 1.71 kV for Lgd = 18 μm. To our knowledge, these values are the best results ever reported for normally-off GaN-based MOSFETs.

Enhancement-mode GaN hybrid MOS-HFETs on Si substrates with Over 70 A operation

We report on the demonstration of enhancement-mode n-channel GaN-based hybrid MOS-HFETs realized on AlGaN/GaN heterostructure on silicon substrates with a large drain current operation. The GaN-based hybrid MOS HFETs realized the threshold voltage of 2.8 V, the maximum drain current of over 70 A with the channel width of 340 mm. This is the best value for an enhancement-mode GaN-based FET. The specific on-state resistance was 16.5 mΩcm2. The breakdown voltage was over 500 V. These results suggest that this structure is a good candidate for power switching applications.

High-power AlGaN/GaN HFETs on Si substrates

In this paper, GaN-based HFET devices on 4-inch Si substrates were fabricated, and the device characteristics were examined. As a result, the maximum drain current was estimated to be over 115 A using MIS-structures. A trade-off between the specific on-resistance (RonA) and the breakdown voltage (Vb) was improved using carbon doped buffer layers, resulting in obtaining RonA=3D 5.9 mΩcm2 and Vb=3D 1730 V simultaneously with the gate-width of a 340 mm. Furthermore, the gate field-plate structure was introduced into MIS-HFET structures. We have examined the suppression of a current collapse phenomenon owing to the combination of the gate field-plate structure and a conductive Si substrate with MIS-HFET devices.