High-current AlInN/GaN field effect transistors



We present a study on AlInN/GaN field effect transistors (FETs) grown by metalorganic chemical vapor phase epitaxy. AlInN can be grown lattice-matched to GaN with an In concentration of 18%. In this study samples with In concentrations ranging from 9.5 to 24%, covering a range from tensely to compressively strained AlInN layers, were grown on GaN layers on Si(111). From Hall effect and capacitance-voltage measurements we find high sheet carrier densities for most of the samples indicating a high electron density at the AlInN/GaN heterointerface. This is also reflected in the behavior of processed FETs. Nearly lattice-matched structures show sheet carrier densities of 3.2 × 1013 cm–2 and mobilities up to ∼406 cm2/Vs. Such Al0.84In0.16N FETs have maximum DC currents of 1.33 A/mm for devices with 1 µm gate length and 100 µm gate width and an output power of 2.5 W/mm at 2 GHz. The best devices with In concentrations of 19% show maximum output powers of 4.1 W/mm at 2 GHz. In contrast to that a compressively strained AlInN layer with an In concentration of 24% leads to a decreased polarization charge at the heterointerface and a low DC current of ∼70 mA/mm. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)