Temperature-Dependent Access Resistances in Large-Signal Modeling of Millimeter-Wave AlGaN/GaN HEMTs

In this paper, a new method for the separate extraction of the temperature-dependent source (R-s) and drain (R-d) access resistances in gallium nitride (GaN) high electron-mobility transistors (HEMTs) by using the definition of access resistances is reported. Based on this method, the temperature-dependent access resistances (TDARs) of a 0.15 mu m gate-length GaN HEMT with unequal gate-source and gate-drain distance are extracted. By integrating the extracted access resistances into a modified Angelov model, the effects of TDARs on millimeter-wave (mmW) large-signal performance of the 0.15 mu m GaN HEMT at different ambient temperatures (i.e., -55 degrees C, 25 degrees C, and 85 degrees C) are investigated. Moreover, the influence of temperature coefficient difference between R-s and R-d due to the asymmetry of the device has been also revealed. The results show that the TDARs have large impact on the large-signal modeling of mmW GaN HEMTs, and the temperature coefficients of R-s and R-d need to be considered separately in the modeling of asymmetric GaN HEMTs. The proposed TDARs extraction method would be useful for accurate modeling of GaN HEMTs at mmW frequencies.