Time-dependent conduction mechanisms in reversed stepped superlattice layers of GaN HEMTs on 200 mm engineered substrates

Abstract

Time-dependent conduction in epitaxial superlattice (SL) strain relief layers of GaN high electron mobility transistors on 200 mm engineered substrates with a poly-AlN core was observed and analyzed. This phenomenon occurs when the devices were operated with substrate bias of similar to-300 V for 10(1)-10(3) s. The formation of the conduction path is related to trap-assisted leakage through the SLs on the engineered substrates; de-trapped carriers spread out vertically and laterally within a portion of the SLs, leading to a higher electrical field across the rest of the layers. This conduction mechanism may be hidden during the devices' normal operation (target 650-1200 V). It could lead to undesired effects during the operation of the devices, such as a time-dependent dynamic R-on. More resistive SLs will potentially reduce the impact of this phenomenon.