Analysis of threshold voltage shift in AlGaN/GaN heterostructure field-effect transistors with different buffer layers

This study applied amethodology for defining the threshold voltage shift (ΔV_TH) transient of AlGaN/GaN heterostructure field-effect transistors (HFETs) to observe the influence of traps in AlGaN/GaN HFETs with different buffer layers: a carbon-doped (C-doped) buffer and an Al_0.05Ga_0.95N back barrier layer. This methodology involves synchronous switching of gate-to-source voltage (V_GS) and drain-to-source voltage (V_DS). Two HFETs demonstrated similar transient behaviors but different trends by enduring various V_DS stress level. For devices with a C-doped buffer layer, the amount of threshold voltage shift becomes saturated with increasing V_DS stress; however, a device with an Al_0.05Ga_0.95N back barrier layer does not. A simulation tool was used to analyze the trap behaviors and close agreement was seen between measured and simulated.