The role of buffer traps (identified as C N acceptors through current DLTS) in the off-state leakage and dynamic Ron of 650V rated GaN-on-Si power devices is investigated. The dynamic Ron is strongly voltage-dependent, due to the interplay between the dynamic properties of the C N traps and the presence of space-charge limited current components. This results in a complete suppression of dyn Ron degradation under HTRB conditions between 420V and 850V.

A strong positive correlation between dynamic Ron and the ionization of buffer traps by injection of electrons from the Si substrate is presented. By exploring different Carbon doping profiles in the epi layers, the substrate buffer leakage is substantially reduced, which in turns results in lower dynamic Ron. The traps in the epi structure are characterized by different electrical techniques such as drain current transient, on-the-fly trapping and ramped back-gating experiments. © 2015 IEEE

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