Delta-doped AlGaN/GaN heterostructure field-effect transistors with incorporation of AlN epilayers

The simulation and experiment results of delta-doped AlGaN/GaN heterostructure field-effect transistors (HFETs) with the incorporation of highly-resistive AlN epilayer are reported. The high quality AlN epilayer is used as the dislocation filter for the HFET structure growth, and the high resistivity of AlN also removes the parasitic conduction related with the GaN bulk buffer. Delta doping can reduce gate leakage, further more, our simulation and growth results demonstrate that delta-doping in the barrier is more effective than uniform doping scheme to increase the sheet electron density. The influence of spacer layer thickness on the electron mobility and sheet electron density is also presented. The DC characterization of the fabricated devices shows our structure has a very high performance with a maximum current ∼ 1 A/mm.