Recent development in flourine-ion-implanted GaN-based heterojunction power devices

In this paper, we report recent progress in the development of the fluorine ion implantation (F-implantation) technique for fabricating enhancement-mode (E-mode) GaN heterojunction power transistors. An integrated gate protection technique and a MIS-HEMT technology have been developed in order to improve the device reliability and make the E-mode GaN power transistors more compatible with standard gate drive ICs that demand large gate swing and low gate leakage. By embedding a small depletion-mode (D-mode) HEMT to the gate electrode, a high-voltage Schottky-gate E-mode HEMT can sustain large input-gate voltage swing (> 20 V) without gate failure and observable shift in the threshold voltage. This gate protection scheme introduces negligible degradation to the switching performance in MHz range, and thus, is suitable for most of the targeted applications of GaN power switches. By integrating the F-implantation technique with SiN_x gate dielectric, high-performance 600 V normally-off GaN MIS-HEMTs with large gate swing, low current collapse and good threshold voltage stability are successfully demonstrated.