1 F NOISE CHARACTERISTICS OF ALGAAS/GAAS HETEROJUNCTION BIPOLAR-TRANSISTOR WITH A NOISE CORNER FREQUENCY BELOW 1 KHZ/

To reduce the low-frequency noise, HBT's with a large emitter size of 120 x 120 mu m(2) are fabricated on abrupt emitter-base junction mater ials without undoped spacer. The HBT's exhibit an internal noise corne r frequency of 100 Hz, which is much lower than about 100 kHz of conve ntional AlGaAs/GaAs HBT's, From the very low noise HBT's, the existenc e of resistance fluctuation 1/f noise is clearly verified by the simpl e comparison of collector current noise spectra with different base te rminations. It is found that, at a high emitter-base forward bias, the resistance fluctuation 1/f noise becomes dominant for shorted base-em itter termination, but the internal 1/f noise dominant for open base. Device design rules for low noise small-feature size HBT, including re sistance fluctuation, are discussed.