Remarkable Current Collapse Suppression in GaN HEMTs on Free-standing GaN Substrates

The current collapse phenomena, particularly the trap-induced threshold voltage shift, was drastically reduced in GaN high-electron-mobility transistors (GaN-HEMTs) fabricated on GaN free-standing substrates. High breakdown voltage of 376 V was achieved and off-state leakage current was also suppressed until a hard breakdown condition. These could be attributed to the improvement of crystal quality in the homoepitaxial GaN layer, that is, reduction in the dislocation density and absence of nucleation layer. GaN-HEMTs on GaN substrates with a gate length of 0.5 mu m exhibited good RF performance with a maximum power added efficiency of 71% with an associated output power of 6.6 W/mm at a 2.45 GHz load-pull measurement. It is evident that GaN-HEMTs on the GaN substrates are promising for driving up a performance of an RF amplifier.