Growth of Crack-Free GaN on Si HEMTs with Fe-Doped GaN Using Un-Doped GaN Interlayer

We show the influence of Fe-doping upon bowing and cracking in GaN-on-Si based high-electron-mobility transistors (HEMTs) and report how to prevent from bowing and cracking. In-situ reflectance measurements revealed that stress relaxation occurred during the growth of GaN:Fe on Al0.25Ga0.75N, resulting in the wafer bowing and cracking. In-situ measurements and transmission electron microscope images showed that the relaxation was caused by the 3D growth of GaN:Fe and the propagation of threading dislocations. To suppress the relaxation, a 100 nm-thick un-doped GaN interlayer was inserted between GaN:Fe and Al0.25Ga0.75N. As a result, a crack-free low-bow surface was obtained for GaN-on-Si HEMTs with GaN:Fe.