Demonstration of low leakage current and high polarization in ultrathin AlN/GaN high electron mobility transistors grown on silicon substrate

High quality AlN/GaN heterostructures grown on silicon substrate are demonstrated. It is found that high carrier concentration can be achieved whereas circular diodes showed a low leakage current up to 200 V reverse bias. 200 nm gate length AlN/GaN transistors exhibited a drain current density of 1.3 A/mm with a pinchoff leakage current below 20 μA/mm and a record GaN-on-silicon extrinsic transconductance of 470 mS/mm. These results demonstrate the possibility to achieve a unique combination of large polarization with a barrier thickness as low as 3 nm while preserving a remarkably low device leakage current without using any gate insulator.