AlGaN/GaN high electron mobility transistors grown on 3C-SiC/Si(111)

The elaboration of Gallium nitride (GaN)-based high electron mobility transistors (HEMTs) structures is comparatively investigated on cubic SiC/Si(111) templates and on silicon substrates. As compared with silicon, 3C-SiC/Si(111) template is less sensitive to the detrimental nitridation effect of ammonia, and it allows a reduction of the stress in GaN films due to both lower lattice and thermal expansion coefficient mismatch. Crack-free GaN layers and AlGaN/GaN HEMTs with total thicknesses exceeding 2 mu m were successfully grown by molecular beam epitaxy on optimized 0.8-mu m-thick 3C-SiC/Si templates elaborated by chemical vapor deposition. A threading dislocation density below 5 x 10(9) cm(-2) and a two-dimensional electron gas with a sheet carrier concentration of 1.1 x 10(13) cm(-2) and an electron mobility of 2050 cm(2)/V s at room temperature have been obtained. The feasibility of the 3C-SiC/Si(111) approach is demonstrated by the structural and electrical quality of these structures, as well as the characteristics of transistors that are at least equivalent to reference transistors realized on bulk silicon substrates. (C) 2008 Elsevier B.V. All rights reserved.