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 μm 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 μm GaN HEMT at different ambient temperatures (i.e., -55 °C, 25 °C, and 85 °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.