On the Origin of Kink Effect in Current-Voltage Characteristics of AlGaN/GaN High Electron Mobility Transistors

An explanation for the observed drain current collapse in AlGaN/GaN high electron mobility transistors is presented. The drain current-voltage (I-V) characteristics which show this undesirable behavior have been modeled using the physics-based ATLAS device simulator by Silvaco. A basic theory for the determination of virtual gate length for a three terminal device has been developed and used in the simulation. The simulated I-V characteristics closely match the experimental results. This paper suggests a model based on formation of a high resistance region under the virtual gate in the 2-D electron gas channel. The resistance of this region changes abruptly at a critical lateral electric field due to application of drain-source voltage. This abrupt change has been found to be a function of channel temperature. The dynamic behavior of this high resistance region has been proposed to be the cause of drain current collapse.