Mitsuru Masuda

Switching Characteristics of GaN HFETs in a Half Bridge Package for High Temperature Applications

AlGaN/GaN heterojunction field effect transistors (HFETs) are expected to be a good candidate for power switching application at high temperatures. We designed and fabricated a discrete HFET package and a half bridge module using the AlGaN/GaN HFETs and SiC Schottky barrier diodes (SBDs) for high temperature applications. The half bridge module exhibited good reliability after 250 C and 400 h high temperature storage. Switching characteristics of the AlGaN/GaN HFET were investigated. Qg x Ron, which shows a figure of merit of switching operation, was more than 10 times better than commercial Si MOSFETs. The switching characteristics of the HFET showed no significant degradation up to 225 C.

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.

High-Temperature Operation of AlGaN/GaN HFET With a Low on -State Resistance, High Breakdown Voltage, and Fast Switching

Improved characteristics of an AlGaN/GaN HFET are reported. In this paper, the authors introduce a new ohmic electrode of Ti/AlSi/Mo and a low refractive index SiNx to decrease the contact resistance and gate leakage current. The AlGaN/GaN HFET showed a low specific resistance of 6.3 mOmega middot cm2 and a high breakdown voltage of 750 V. The switching characteristics of an AlGaN/GaN HFET are investigated. The small turn-on delay of 7.2 ns, which was one-tenth of Si MOSFETs, was measured. The switching operation of the HFET showed no significant degradation up to 225 degC

288 V-10 V DC- DC Converter Application Using AlGaN/GaN HFETs

We report on the 288 V-10 V DC- DC converter circuit using AlGaN/GaN HFETs for the first time. The AlGaN/GaN HFET with a large current and a high breakdown voltage operation was fabricated. That is, the maximum drain current was over 50 A, and the minimum on-resistance was 70 mohm. The breakdown voltage was over 600 V. A DC-DC down-converter from input DC 288 V to output DC 10 V was fabricated using these HFETs. It was confirmed that the switching speed of the AlGaN/GaN HFET was faster than that of Si MOSFET. The DC-DC down-converter was fabricated using these HFETs. This converter was composed of a full bridge circuit using four n-channel AlGaN/GaN HFETs. In the case of AlGaN/GaN HFET, a gate switching wave (Vgs) and source-drain wave (Vds) were abrupt compared with those of using Si MOSFETs. In both cases, a stable and constant output DC 10V was also obtained and the conversion efficiency of the converters with AlGaN/GaN HFETs was 84%.

Discrete and Half Bridge Module using GaN HFETs for High Temperature Applications more than 200°C

AlGaN/GaN HFETs are expected to be a good candidates for power switching application at high temperatures. We optimized the fabrication process of the AlGaN/GaN HFET. A low specific on-state resistance of 6.3 mOmegacm2 and a large breakdown voltage of 600 V were achieved at 225degC. We also designed and fabricated a half bridge module using the AlGaN/GaN HFETs and SiC SBDs. Switching characteristics of the AlGaN/GaN HFET were investigated. The small turn-on delay of 7.2 nsec, which is 1/10 of Si MOSFET, was observed. The switching characteristics of the HFET showed no significant degradation up to 225degC.

High Temperature Operation at 225°C of a Half Bridge Module using GaN HFETs

AlGaN/GaN HFETs are expected to be a good candidates for power switching application at high temperatures. We optimized the fabrication process of the AlGaN/GaN HFET. A low specific on-state resistance of 6.3 mOmegacm2 and a large breakdown voltage of 600 V were achieved at 225degC. We also designed and fabricated a half bridge module using the AlGaN/GaN HFETs and SiC SBDs. Switching characteristics of the AlGaN/GaN HFET were investigated. The small turn-on delay of 7.2 nsec, which is 1/10 of Si MOSFET, was observed. The switching characteristics of the HFET showed no significant degradation up to 225degC

Verification efficiency of electric coupling wireless power transfer in water

This paper focuses on efficiency improvement of electric coupling wireless power transfer in water. The S-Parameters of the parallel plate electric coupler are clarified by using 3D simulation and measurement. Based on the result, the frequency characteristic of the maximum efficiency of the electric coupling wireless power transfer in fresh water was revealed by the simulated and measured results. Finally, over 60% of power transfer efficiency is experimentally achieved.

Reduce of electric ner-field intensity by a shield box in wireless power transfer via field resinance coupling

Wireless Power transfer using electric field can realize highly efficient electrical power transmission and the transmission units are thin and light. However, the transmission system produces large electric field intensity and the electric field noise can make other electronic devices malfunction. A shield box is greatly effective to reduce the electric intensity 60dB without a decline of transmission efficiency. The distance between the shield box and the transmission unit should be a half of the transmission distance between a transmitter and a receiver. The shield box can attenuate the intensity behind the box less than 100V/m in case of 1kW transmission.

Wireless Power Transfer via Electric Field Resonance Coupling

Wireless power transfer systems using electric fields have been investigated mainly for power transfer over extremely close regions. Using an electromagnetic field simulator, we have made a prototype of an LC series type resonance coupler made from a coil and electrode. When the distance between the transmission and reception couplers was varied, it was found that a transfer efficiency of 90% or more was achieved at a distance of 180 mm. Also a large power transfer test was carried out in which it was found that it was possible to transfer 838 W of power.