1/F NOISE IN ALGAAS/GAAS HBTS USING ULTRASENSITIVE CHARACTERIZATION TECHNIQUES FOR IDENTIFYING NOISE MECHANISMS

The 1/f noise characteristics and mechanisms of GaAs/AlGaAs HBT's are studied using conventional short circuit current measurements (S(IC)(f) and S(IB)(f)) and an indirect highly sensitive technique based on noise figure characterization. The S(IC)(f) and S(IB)(f) follows a 1/f dependence at low frequencies, for moderate bias conditions. A Lorentz component is found in the spectra. The base resistances are obtained by approximating them to the correlation resistances and range from 17-OMEGA to 63-OMEGA. The intrinsic noise sources are studied using a simple model employing two internal, uncorrelated noise sources. These sources are similar to the S(IC)(f) and S(IB)(f) at moderate bias conditions. However, the intrinsic collector noise differs from S(IC)(f) at low bias conditions.