Low-frequency noise characteristics of UHV/CVD epitaxial Si- and SiGe-base bipolar transistors

We report the first measurements of low -frequency noise in high-performance, UHV/CVD epitaxial Si- and SiGe-base bipolar transistors. The magnitude of the noise power spectral density at fixed frequency for both Si and SiGe devices is comparable for similar bias, geometry, and doping conditions, indicating that the use of strained SiGe alloys does not degrade transistor noise performance. The best recorded values of noise corner frequency were 480 Hz and 373 Hz for the Si and SiGe transistors, respectively for multi-stripe devices with an emitter area of 0.5 x 10.0 x 3 mu m(2). A functional dependence of the noise power spectral density on base current for both device types of I-B(1.90) was observed, and noise measurements as a function of device geometry suggest that the contributing noise sources are uniformly distributed across the emitter of the transistors, not at the emitter periphery.