2.3 nm barrier AlN/GaN HEMTs with insulated gates

Ultra‐shallow channel AlN/GaN high electron mobility transistor (HEMT) structures with a 2.3 nm AlN barrier were grown by plasma‐assisted molecular beam epitaxy (PAMBE) on sapphire substrates. They exhibit 2‐D electron gas densities of ∼ 1.4 x 1013 cm–2 and electron hall mobilities of ∼ 1600 cm2/Vs. Insulated‐gate stacks of SiNx/Al2O3/Ni/Au were used to suppress the gate leakage current, which is found to largely stem from dislocation‐assisted leakage paths. AlN/GaN HEMTs with 250 nm gate length showed DC output current densities of up to 1.6 A/mm, transconductances of ∼ 300 mS/mm, and extrinsic ft/fmax of 24/52 GHz. These performance metrics demonstrate that these ultra‐shallow channel AlN/GaN heterostructures hold a lot of promises for high‐power high‐frequency device applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)