Temperature dependence and electrical properties of dominant low-frequency noise source in SiGe HBT

The temperature dependence and electrical properties of the dominant low-frequency noise source in a SiGe HBT have been investigated. By employing a temperature variation of the device to get a variation of the base or collector current independently of each other, it is shown that the dominant noise source is strongly dependent on the collector current, but only weakly dependent on the base current. A modified Ebers-Moll model is presented that accounts for the collector current dependence of the dominant noise source and simultaneously accounts for the temperature dependence of /spl beta/. Using the modified Ebers-Moll model, the understanding of the physical positioning of the noise source is simplified.