High breakdown AlGaN/GaN HEMTs employing double metal structure

We have proposed and fabricated AlGaN/GaN HEMTs employing a nickel oxide (NiO_X) based double metal structure which showed a stable reverse blocking characteristics. The leakage current of the proposed device was decreased by four orders of magnitude. The leakage current of the conventional device at room temperature was 80 μA/mm while that of the proposed device was 16.6 nA/mm. In the high temperature reverse bias (HTRB) test, the ratio of the gate leakage current to the total leakage was decreased with operational temperature. From experimental results of the HTRB test, it was demonstrated that NiO_X-based double gate contact was thermally and electrically robust and made a significant contribution to stable blocking operation. In terms of the breakdown behavior, the device with a double metal structure successfully suppressed the premature breakdown while conventional one showed a soft breakdown behavior. The measured breakdown voltage (V_BR) of the conventional device was 1310 V while V_BR of the proposed device was 1480 V with almost no walkout. The stable reverse blocking characteristics of the proposed device was attributed to the resistance switching property of the nickel oxide film and the high barrier height established between thermally oxidized nickel film and surface of the device.