Degradation mechanisms of Mg-doped GaN/AlN superlattices HEMTs under electrical stress

摘要

GaN-based high electron mobility transistors (HEMTs) have exhibited great application prospects in power and radio frequency devices, thanks to the superior properties of GaN. Despite the significant commercialization progress, the reliability of GaN-based HEMTs remains a challenge. This work experimentally investigates the time-dependent degradation of Mg-doped GaN/AlN superlattice HEMTs under both OFF-state and SEMI-ON-state bias conditions and proposes that GaN/AlN superlattices as a barrier can solve the V-th instability issues of GaN HEMTs under OFF-state and SEMI-ON-state bias conditions. On the one hand, in the SEMI-ON-state, the hot electron effect leads to the degradation of I-g, g(m,max), and I-d,I- sat to varying degrees. However, the as-prepared GaN-based HEMTs exhibit excellent V-th stability (almost no change) under hot electron injection, on the account of the excellent two-dimensional electron gas confinement in the GaN/AlN superlattice structure. On the other hand, in the OFF-state, positive V-th shift (about 0.12 V) is induced by the hole emission in the GaN/AlN superlattice structure under reverse bias stress. In addition, the stress-induced destruction of MgO gate dielectric gives rise to the gate leakage, which increases by 2 orders of magnitude and triggers an irreversible degradation (about 10%) of the g(m,max). These results are expected to provide a solution to the V-th instability of GaN HEMTs. Published under an exclusive license by AIP Publishing.

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