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

Abstract

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 0.90×1013to1.64×1013cm−2 with corresponding electron mobilities of 1600 and 1410cm2∕Vs, respectively. The 10K mobility reached 17600cm2∕Vs for the nearly lattice-matched Al0.82In0.18N∕AlN∕GaN heterostructure with a sheet carrier density of 9.6×1012cm−2. For comparison, the AlInN∕GaN heterostructure without the AlN spacer exhibited a high sheet carrier density (2.42×1013cm−2) with low mobility (120cm2∕Vs) at room temperature. The high mobility in our samples is in part attributed to ∼1nm AlN spacer which significantly reduces the alloy scattering as well as provides a smooth interface. The HFETs having gate dimensions of 1.5×40μm2 and a 5μm source-drain separation exhibited a maximum transconductance of ∼200mS∕mm with good pinch-off characteristics and over 10GHz current gain cutoff frequency.