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 homo-epitaxial 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 μm 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.