AlN/GaN insulated-gate HEMTs with 2.3 A/mm output current and 480 mS/mm transconductance

High-electron mobility transistors (HEMTs) based on ultrathin AlN/GaN heterostructures with a 3.5-nm AlN barrier and a 3-nm Al2O3 gate dielectric have been investigated. Owing to the optimized AlN/GaN interface, very high carrier mobility (similar to 1400 cm(2)/V . s) and high 2-D electron-gas density (similar to 2.7 x 10(13)/cm(2)) resulted in a record low sheet resistance (similar to 165 Omega/sq). The resultant HEMTs showed a maximum dc output current density of similar to 2.3 A/mm and a peak extrinsic transconductance g(m,ext) similar to 480 mS/mm (corresponding to g(m,int) similar to 1 S/mm). An f(T)/f(max) of 52/60 GHz was measured on 0.25 x 60 mu m(2) gate HEMTs. With further improvements of the ohmic contacts, the gate dielectric, and the lowering of the buffer leakage, the presented results suggest that, by using AlN/GaN heterojunctions, it may be possible to push the performance of nitride HEMTs to current, power, and speed levels that are currently unachievable in AlGaN/GaN technology.