In this study, AlGaN/GaN high-electron-mobility transistors with a 5-nm p-GaN cap layer were investigated to compare their performance under various activation conditions. Specifically, p-GaN cap layers were activated using rapid thermal annealing at 700°C for 5, 10, and 15 min in an N2 environment before device fabrication. The gate leakage current reduced considerably when the p-GaN cap layer activation time was longer. The measured on/off current ratio was improved to 9 × 107 for a Schottky-gate device with 15-min annealing time. The breakdown voltage was increased using the activated p-GaN cap layer. In pulsed I–V measurements, the device with the p-GaN cap layer with a 15-min activation time exhibited less current dispersion.
Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) have the advantages of high-frequency switching capability and the capability to withstand high temperatures, which are suitable for switching devices in a direct current (DC) solid state circuit breaker (SSCB). To guarantee fast and reliable action of a 400 V DC SSCB with SiC MOSFET, circuit design and prototype development were carried out. Taking 400V DC microgrid as research background, firstly, the topology of DC SSCB with SiC MOSFET was introduced. Then, the drive circuit of SiC MOSFET, fault detection circuit, energy absorption circuit, and snubber circuit of the SSCB were designed and analyzed. Lastly, a prototype of the DC SSCB with SiC MOSFET was developed, tested, and compared with the SSCB with Silicon (Si) insulated gate bipolar transistor (IGBT). Experimental results show that the designed circuits of SSCB with SiC MOSFET are valid. Also, the developed miniature DC SSCB with the SiC MOSFET exhibits faster reaction to the fault and can reduce short circuit time and fault current in contrast with the SSCB with Si IGBT. Hence, the proposed SSCB can better meet the requirements of DC microgrid protection.
This study discusses the impact of a p-GaN backgate structure on the DC characteristics of AlGaN/GaN HEMTs. AlGaN/GaN HEMTs with a p-GaN backgate layer showed reduction of leakage current and positive shift of threshold voltage while applying negative backgate bias. The shift of threshold voltage was 0.55 V, and reduction of off-state leakage current was 73.1% while backagte bias was -14 V. The on/off current ratio was in the range of 10 7 with backgate bias. It is possible to operate an AlGaN/GaN HEMT in both D-and E-modes with suitable epitaxial layer design using a p-GaN backagte structure.
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