An 80W AlGaN/GaN heterojunction FET with a field-modulating plate

An AlGaN/GaN heterojunction FET with a field-modulating plate (FP) has been fabricated on a SiC substrate. The gate breakdown voltage (BV/sub gd/) was improved from 50V to 160V by introducing an FP electrode. The highest BV/sub gd/ was obtained with an FP length of 1.0 /spl mu/m. A 4mm-wide unit-cell FET exhibited 32.5W (8.1W/mm) output power, 62% power-added efficiency, and 12.4 dB linear gain at a drain bias of 41V. The linear gain decreased with increasing the FP length, but the difference in the linear gain among FETs with various FP lengths decreased with increasing the drain bias. To the best of our knowledge, a power density of 8.1W/mm is the highest for GaN based FETs with over 1mm gate width. For a 24mm-wide 6-cell FET, an output power of 80.0W (3.3W/mm) was obtained with a linear gain of 8.5dB and a power-added efficiency of 42% at a drain bias of 31V.