차세대 전력 스위치용 1.5 kV급 GaN 쇼트키 장벽 다이오드

Abstract

The O₂ annealing technique has considerably suppressed the leakage current of GaN power devices, but this forms NiO at Ni-based Schottky contact with increasing on-resistance. The purpose of the present study was to fabricate 1.5 ㎸ GaN Schottky barrier diodes by improving O₂-annealing process and GaN buffer. The proposed O₂ annealing performed after alloying ohmic contacts in order to avoid NiO construction. The ohmic contact resistance (R<SUB>C</SUB>) was degraded from 0.43 to 3.42 Ω-㎜ after O₂ annealing at 800 ℃. We can decrease RC by lowering temperature of O₂ annealing. The isolation resistance of test structure which indicated the surface and buffer leakage current was significantly increased from 2.43×10? to 1.32×10<SUP>13</SUP> Ω due to O₂ annealing. The improvement of isolation resistance can be caused by formation of group-Ⅲ oxides on the surface. The leakage current of GaN Schottky barrier diode was also suppressed from 2.38×10<SUP>-5</SUP> to 1.68×10<SUP>-7</SUP> A/mm at ?100 V by O₂ annealing. The GaN Schottky barrier diodes achieved the high breakdown voltage of 700, 1400, and 1530 V at the anode-cathode distance of 5, 10, and 20 ㎛, respectively. The optimized O₂ annealing and 4 ㎛-thick C-doped GaN buffer obtained the high breakdown voltage at short drift length. The proposed O₂ annealing is suitable for next-generation GaN power switches due to the simple process and the low the leakage current.