High Power Normally-Off GaN MOSFET on Si Substrate

GaN has superior physical properties for power devices, such as a high critical breakdown voltage, superior carrier transport properties, and good thermal dissipation. For GaN-based transistors, AlGaN/GaN HFETs with lower on-state resistances and higher breakdown voltages have been reported [1]. However, the operation of AlGaN/GaN HFETs was essentially normally-on mode, and then normally-off operation is strongly required for power switching applications. In this work, normally-off n-channel GaN-based MOSFETs on Si substrates have been demonstrated. The fabricated GaN MOSFETs using an ion implantation technique as shown in Fig. 1 show good normally-off operation with threshold voltage of 2.7 V, the maximum output current of over 3.5 A with the channel length of 4 μm and the channel width of 16 mm, respectively, and a high-temperature operation up to 300C. Furthermore, AlGaN/GaN hybrid MOSHFETs were fabricated. Fig. 2 shows the schematic crosssectional view of the AlGaN/GaN hybrid MOS-HFET. The MOS-HFET has the merits of both a MOS channel and an AlGaN/GaN heterostructure with high mobility two dimensional electron gases. Fig. 3 shows the output characteristics of the MOS-HFET with the channel length of 2 μm and the channel width of 340 mm, respectively. The maximum drain current of over 100 A is performed. The specific on-state resistance is 9.3 mΩ-cm. The fabricated MOS-HFETs also exhibit good normally-off operation and the breakdown voltage of over 600 V. These results indicate that AlGaN/GaN hybrid MOSHFET structure is a promising candidate for obtaining devices with a lower on-state resistance and a high breakdown voltage. [1] N. Ikeda et al., Proc. IPEC, pp. 1018, 2010. -20 0 20 40 60 80 100 120