P-doped region below the AlGaN/GaN interface for normally-off HEMT

Development of a new design for enhancement-mode AlGaN/GaN HEMT is presented. The normally-off operation was achieved by burying a p-GaN region below the AlGaN/GaN interface only below the gate. Simulation results show that the proposed technique is capable of shifting the threshold voltage to positive values, making the HEMT normally-off. To address the advantages and drawbacks of the proposed structure a comparison with the normally-off Gate Injection Transistor (GIT) was performed. The proposed structure seems to be more effective when it comes to the p-doping concentration required to achieve normally-off operation and offers superior confinement for the two dimensional electron gas. On the other hand, the low forward gate voltage limits the increase of the threshold voltage.