Characterization and modeling of thermal effects in sub-micron InP DHBTs

S-parameter measurements performed on 400GHz InP DHBTs, with 250nm and 400nm wide emitters, show that an 8-10% increase in peak f_T can be achieved when the ambient temperature is reduced from +25°C to -50°C. This strong temperature dependence of device performance indicates that thermal modeling plays a critical role in device and circuit design. Using the Synopsys® DESSIS simulator, a 3D thermal model was calibrated to these sub-micron 400GHz InP DHBTs for use in technology development. The 3D model is sufficiently complex to allow the thermal de-embedding of pads; projection of R_TH to higher dissipated powers; and estimates of cooperative heating. These three features allow the 3D model to go beyond the data that can be acquired by direct measurement, and lead to a more accurate value of R_TH for compact models.