Reliability issues of gate oxides and p-n junctions for vertical GaN metal-oxide-semiconductor field-effect transistors (Invited)

We focus on reliability issues of gate oxides and p-n junctions to realize vertical GaN metal-oxide-semiconductor field-effect transistors (MOSFETs). An annealed AlSiO gate oxide on GaN displayed a lifetime of over 20 years at 150 degrees C and suppressed positive bias instability in MOSFETs. The key to high channel mobility and stability under positive gate bias is the interface structure designed to minimize oxide border traps. We also evaluated the reliability of GaN p-n diodes (PNDs) on freestanding GaN substrates with different threading dislocation densities. The reverse leakage for PNDs involving threading dislocations was explained by variable-range hopping, while the reverse leakage for dislocation-free PNDs was dominated by band-to-band tunneling. The fabricated PNDs demonstrated excellent robustness under high-temperature reverse bias. However, after continuous forward current stress, reverse leakage pathways were formed at threading screw dislocations, which should be minimized in future GaN substrates.

Automated summary

We investigated the reliability issues of gate oxides and p-n junctions in vertical GaN metal-oxide-semiconductor field-effect transistors (MOSFETs). A specially designed AlSiO gate oxide on GaN showed excellent stability and a projected lifetime of over 20 years at high temperatures. The reliability of GaN p-n diodes (PNDs) with different threading dislocation densities was also evaluated. The fabricated PNDs demonstrated robustness under high-temperature reverse bias, but reverse leakage pathways were formed at threading screw dislocations after continuous forward current stress, which should be minimized in future GaN substrates.