Ionization effect on SiGe HBT power limitation in the millimeter wave frequency range

Load-pull measurements at 94 GHz are performed on last-generation SiGe HBTs, in order to understand the origins of the power constraints in the presence of millimeter-wave excitations. A very accurate HICUM model is used for the devices under test to correlate measurement results and physical phenomena. In such a way, we investigate the ionization and self-heating effects on the power limitations in high-frequency nonlinear device operation. We show that the impact ionization is the major limitation on power improvement.