Compositional variation of nearly lattice-matched InAlGaN alloys for high electron mobility transistors

Quaternary InAlGaN semiconductors with AlN mole fractions between 40% and 81% and respective InN contents of 7% and 19% including InAlN as a ternary border case have been grown by plasma-assisted molecular beam epitaxy. The electron mobility in InAlGaN-based heterostructures increases with Ga concentration in the barrier up to 1460 cm(2)/V s at a sheet electron density of 1.9x10(13) cm(-2). An advanced spacer comprising an AlN/GaN/AlN triple-layer sequence is inserted between the GaN-buffer and the InAlGaN-barrier. Transistors with thin quaternary barrier show a large current density of 2.3 A/mm and an excellent transconductance of 675 mS/mm. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456561]