High electron mobility in nearly lattice-matched AlInN/AlN/GaN heterostructure field effect transistors

High electron mobility was achieved in Al1-xInxN/AlN/GaN (x=0.20-0.12) heterostructure field effect transistors (HFETs) grown by metal-organic chemical vapor deposition. Reduction of In composition from 20% to 12% increased the room temperature equivalent two-dimensional-electron-gas density from 0.90x10(13) to 1.64x10(13) cm(-2) with corresponding electron mobilities of 1600 and 1410 cm(2)/V s, respectively. The 10 K mobility reached 17 600 cm(2)/V s for the nearly lattice-matched Al0.82In0.18N/AlN/GaN heterostructure with a sheet carrier density of 9.6x10(12) cm(-2). For comparison, the AlInN/GaN heterostructure without the AlN spacer exhibited a high sheet carrier density (2.42x10(13) cm(-2)) with low mobility (120 cm(2)/V s) at room temperature. The high mobility in our samples is in part attributed to similar to 1 nm AlN spacer which significantly reduces the alloy scattering as well as provides a smooth interface. The HFETs having gate dimensions of 1.5x40 mu m(2) and a 5 mu m source-drain separation exhibited a maximum transconductance of similar to 200 mS/mm with good pinch-off characteristics and over 10 GHz current gain cutoff frequency. (c) 2007 American Institute of Physics.