On 1/F Noise in Polysilicon Emitter Bipolar Transistors: Coherence between Base Current Noise and Emitter Series Resistance Noise

The 1/f noise in polysilicon emitter bipolar transistors is investigated The main 1/f noise source proved to be located in the oxide layer. This source causes both 1/f noise in the base current S
I
b
and 1/f noise in the emitter series resistance S
r
e
. The 1/f noise is ascribed to barrier height fluctuations of the oxide layer resulting in transparency fluctuations for both minority and majority carriers in the emitter, giving rise to S
I
b
and S
r
e
, respectively. This model predicts S
I
b
and S
r
e
to be correlated. Our experimental results show a correlation factor in the range of 0.3 to 0.5. The deviation from full correlation is ascribed to local inhomogeneities in the oxide layer.