AlInN/GaN HEMTs on sapphire: dc and pulsed characterisation

Abstract

Lattice-matched Al0.83In0.17N/GaN high electron mobility transistors (HEMTs) grown by MOCVD on sapphire substrate were investigated. The transport properties of the 2DEG at room temperature were characterised by sheet carrier concentrations up to 2.0×1013 cm-2 at a mobility of 1450 cm2/Vs. Unpassivated devices with gate lengths of LG = 1 μm and a gate-drain spacing of 5 μm exhibit maximum drain current densities of 1.2 A/mm at VGS = 2 V and extrinsic transconductances of 243 mS/mm, respectively. The small-signal behaviour is characterised by a current gain cutoff frequency fT = 13 GHz and a maximum frequency of oscillation fmax = 29 GHz, respectively. Pulsed I-V measurements from different quiescent bias points reveal dispersion effects resulting in a partial drain current collapse. A SiN passivation was found not to alleviate these effects. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.