Proceedings Article | 15 February 2008
Proc. SPIE. 6894, Gallium Nitride Materials and Devices III
KEYWORDS: Polarization, Scattering, Indium, Gallium nitride, Aluminum, Aluminum nitride, Field effect transistors, Metalorganic chemical vapor deposition, Heterojunctions, Temperature metrology
In AlGaN/GaN heterostructure field effect transistors (HFETs), two-dimensional-electron-gas (2DEG), induced by
strong piezoelectric and spontaneous polarization field, has high sheet density, and can be tuned up to 5 ×1013 cm-2 with pure AlN barrier.[Appl. Phys. Lett. 90, 182112 (2007)].For Al compositions larger than 40%, due to the large lattice mismatch between GaN and AlGaN, strain-related issues significantly reduce the mobility for these high sheet carrier densities. Recently, using nearly lattice-matched AlInN/GaN to improve the performance of HFETs has been studied
theoretically and experimentally. A high sheet density (2.42 ×1013 cm2) with >1000 cm2/Vs mobility has been reported by inserting an AlN spacer layer between the AlGaN barrier and GaN channel. However, low-temperature mobilities for AlInN/GaN HFETs are much lower than those for AlGaN/GaN HFETs. In this paper, we study the Al1-xInxN/AlN/GaN (x=0.20 - 0.12) (HFETs) grown by metalorganic chemical vapor deposition. Reduction of In composition from 20% to
12% increased the room temperature equivalent two-dimensional-electron-gas (2DEG) density from 0.90×1013 cm-2 to 1.64 ×1013 cm-2 with corresponding electron mobilities of 1600 cm2/Vs and 1410 cm2/Vs. Furthermore, at 10 K, the mobility reached 17,600 cm2/Vs with a sheet density 9.6 ×1012 cm-2 for the nearly lattice-matched Al0.82In0.18N
/AlN/GaN heterostructure. The HFETs having 1 μm gate length exhibited a maximum transconductance of ~ 250 mS/mm with good pinch-off characteristics.
