1/f noise characteristics of AlGaAs/GaAs heterojunction bipolar transistor with a noise corner frequency below 1 kHz

To reduce the low-frequency noise, HBTs with a large emitter size of 120×120 μm² are fabricated on abrupt emitter-base junction materials without undoped spacer. The HBTs exhibit an internal noise corner frequency of 100 Hz, which is much lower than about 100 kHz of conventional AlGaAs/GaAs HBTs. From the very low noise HBTs, the existence of resistance fluctuation 1/f noise is clearly verified by the simple comparison of collector current noise spectra with different base terminations. It is found that, at a high emitter-base forward bias, the resistance fluctuation 1/f noise becomes dominant for shorted base-emitter termination, but the internal 1/f noise dominant for open base. Device design rules for low noise small-feature size HBT, including resistance fluctuation, are discussed.