Vertical device operation of AlGaN/GaN HEMTs on free-standing n-GaN substrates

We report on the demonstration of normally off and normally on vertical AlGaN/GaN high electron mobility transistors (HEMTs). The normally off device shows the threshold voltage of 1.6 V. The normally on device shows the normalized on resistance of 1.48 mOmega-cm² and the maximum drain current density of 3.9 kA/cm². Before then, the dependence of threshold voltage on the thickness of n-GaN in the structure of AlGaN/n-GaN/p-GaN was studied experimentally.