Breakdown voltage improvement of enhancement mode AlGaN/GaN HEMT by a novel step-etched GaN buffer structure

A research on breakdown voltage improvement of the enhancement mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMT) has been carried out. A novel step-etched GaN buffer structure combined with a thin GaN buffer is studied by simulating. Both the thin GaN buffer and the step-etched GaN structure can improve the breakdown voltage. The thin GaN buffer can reduce the conductivity as well as alleviate the vertical electric field. And the step-etched GaN structure can form two electric field peaks and thus decrease the original one. With the same gate-drain length of 7 μm, the optimized structure increases the breakdown voltage from 316 V to 1487 V, and the specific on-state resistance is obtained to be 2.718 mΩ•cm2 which is the similar to conventional GaN HEMT, and the calculated FOM is improved by more than 20 times. These results indicate that the novel step-etched GaN buffer structure can improve the breakdown voltage without compromising the output characteristics.