Impact of the field induced polarization space‐charge on the characteristics of AlGaN/GaN HEMT: Self‐consistent simulation study

Abstract

AbstractUsing self‐consistent numerical simulation we have studied the impact of the field induced polarization on the characteristics of AlGaN/GaN high electron mobility transistors (HEMTs). The strain induced by external electric fields is on top of the built‐in strain due to lattice mismatch. It has been suggested that this additional strain can play a role in device degradation and failure (J. Joh and J. del Alamo, Mechanisms for Electrical Degradation of GaN High‐Electron Mobility Transistors, IEDM Tech. Dig., pp. 415–418, Dec. (2006) [1]). The study is carried out using commercial TCAD tools carefully calibrated against the measured characteristics of 0.25 μm physical gate length transistors. A coupled model for piezoelectric materials, including the impact of the field, is used to determine the strain and thus the polarization in the device. The spatial charge distribution is derived from the gradient of the polarization and is fed back self‐consistently to the simulator. Results with and without the field‐induced polarization are compared and discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)