Ultrafast Thermoreflectance Imaging and Electrothermal Modeling of β-Ga₂O₃ MESFETs

We investigated the thermal characteristics of a recently developed delta-doped $\beta $ -Ga2O3 MESFET using thermoreflectance imaging technique, which enabled temperature measurement with ~250 nm spatial and ~400 ns temporal resolution. We measured the temperature contours on source, drain and gate pads, and estimated peak temperature at different bias conditions, and calculated the thermal time constants of these devices, which can be used to predict their transient thermal behavior. The steady-state temperature is measured to be ~199° C at the gate-center at power =2.56W/mm. A 3-D thermal model combined with a device thermodynamic carrier transport model, which is in good agreement with measurements, was used to predict the temperature profile inside the device. Our analysis establishes that the temperature measured at the gate-center is lower than the overall peak temperature in the device, and the difference between peak and gate-center temperature is higher for the lower gate-voltages at similar power.