Breakdown Enhancement and Current Collapse Suppression by High-Resistivity GaN Cap Layer in Normally-Off AlGaN/GaN HEMTs

In this letter, a device structure of high-resistivity-cap-layer HEMT (HRCL-HEMT) is developed for normally-off p-GaN gate HEMT toward high breakdown voltage and low current collapse. It demonstrates that the breakdown capability and current collapse of the device were effectively improved due to the introduction of a thick HR-GaN cap layer. The fabricated HRCL-HEMT exhibits a high breakdown voltage of 1020 V at I-DS = 10 mu A/mm with the substrate grounded. Meanwhile, the qdynamic R-on is only 2.4 times the static R-on after off-state V-DS stress of 1000 V with the substrate grounded (the OFF to ON switching time interval is set to 200 mu s).