Temperature and Bias Dependence of the DC and RF Characteristics of a 150 nm AlGaN/GaN-on-SiC HEMT for Microwave Applications.

We examine the bias- and temperature-dependent direct current, radio frequency, and equivalent-circuit characteristics of a 150 nm AlGaN/GaN/SiC high-electron-mobility transistor (HEMT) for high-frequency applications. DC and S-parameter measurements on the wafer were conducted under various gate-bias settings within a varying thermal condition (-40 °C to 150 °C). The findings suggest a distinct decrease in drain current and transconductance with rising temperature, mostly attributed to heightened carrier dispersion and self-heating effects. At Vds = 15 V, the Ids decreases from 247.63 mA at -40 °C to 142.94 mA at 150 °C. The maximum transconductance decreases from approximately 56.5 mS to 31.5 mS. The assessed thermal resistance varies from 6.3 °C·mm/W to 11 °C·mm/W, signifying an increasing thermal limitation at elevated temperatures. The device has a point at which the temperature coefficient is zero at Vgs = -7.0 V, where the threshold-voltage shift and mobility degradation counterbalance one another. Small signal investigation indicates that ft decreases from approximately 53 GHz to 39 GHz, whereas fmax declines from 107 GHz to 74 GHz within this temperature range. The derived equivalent-circuit characteristics demonstrate the temperature sensitivity of intrinsic capacitances, resistances, transconductance, and delay components, but extrinsic capacitances and inductances exhibit comparatively lower temperature sensitivity. The measured and modeled S-parameters are in strong agreement, hence validating the extraction methodology. The findings may serve as valuable guidance for bias optimization and thermally conscious RF circuit design with GaN HEMT technology.