Split-p-GaN Gate HEMT With Suppressed Negative Vth Shift and Enhanced Robustness Against False Turn-On

Abstract

In the development of the Schottky-type p-GaN gate HEMT, the instable ${V}_{\text {th}}$ is always a highlighted problem. Under high ${V}_{\text {DS}}$ bias, the potential of the floating p-GaN can be raised by the gate/drain coupled barrier lowering (GDCBL) effect, inducing a noticeable negative ${V}_{\text {th}}$ shift. During the fast switching operation, the negative ${V}_{\text {th}}$ shift severely aggravates the false turn-on problem. In this work, a split-p-GaN gate HEMT (SPG-HEMT) is demonstrated to effectively suppress the drain-induced negative ${V}_{\text {th}}$ shift, enhancing the robustness against false turn-on. At ${V}_{\text {DS}} =100$ V, the conventional p-GaN gate HEMT (Conv-HEMT) suffers a negative ${V}_{\text {th}}$ shift of −0.33 V, while the SPG-HEMT exhibits only a minimal ${V}_{\text {th}}$ shift of −0.07 V. In the SPG-HEMT, the GDCBL effect takes place only for the p-GaN near the drain side (p $_{{2}}\text {)}$ ; the p-GaN near the source (p $_{{1}}\text {)}$ is isolated from p2 via the gate/p-GaN Schottky junctions, and the influence of drain bias upon p1 is shielded by p2. Then, the impact of negative ${V}_{\text {th}}$ shift on false turn-on is evaluated by a half-bridge switching circuit. Due to the obvious negative ${V}_{\text {th}}$ shift, the Conv-HEMT is falsely turned on when the ${V}_{\text {GS}}$ ringing peak is still much lower than the static threshold voltage ( ${V}_{{\mathrm {th0}}})$ . In contrast, the SPG-HEMT starts to show false turn-on signal only when the ${V}_{\text {GS}}$ ringing peak is near ${V}_{{\mathrm {th0}}}$ . Overall, the unique device structure of the SPG-HEMT leads to a negligible negative ${V}_{\text {th}}$ shift and enhances the robustness against false turn-on.