Thermal effect in SiGe HBTs

In order to make competitive RF circuit designs, SiGe HBTs are being pushed to their limits by ever higher collector voltages. Under these extreme conditions, self-heating of the device is a growing concern. As a consequence of self-heating, the HBT may become instable due to thermal runaway and even lead to device breakdown. The thermal behavior of SiGe HBTs and the working limits of the devices under self-heating were studied experimentally in this project.
The thermal resistances of various geometries were extracted from both measurement and simulation, and compared with the values in existing HBT transistor model ‘Mextram’.
The electrothermal instability of SiGe HBTs were studied by measuring the stable operating area of both low-voltage (LV) and high-voltage (HV) device at DC and different pulse widths.