Breakdown mechanisms in AlGaN/GaN high electron mobility transistors with different GaN channel thickness values

In this paper, the off-state breakdown characteristics of two different AlGaN/GaN high electron mobility transistors (HEMTs), featuring a 50-nm and a 150-nm GaN thick channel layer, respectively, are compared. The HEMT with a thick channel exhibits a little larger pinch-off drain current but significantly enhanced off-state breakdown voltage (BVoff). Device simulation indicates that thickening the channel increases the drain-induced barrier lowering (DIBL) but reduces the lateral electric field in the channel and buffer underneath the gate. The increase of BVoff in the thick channel device is due to the reduction of the electric field. These results demonstrate that it is necessary to select an appropriate channel thickness to balance DIBL and BVoff in AlGaN/GaN HEMTs.