1/ < e1 > f < /e1 > noise in n-p-n GaAs/AlGaAs heterojunction bipolar transistors:iImpact of intrinsic transistor and parasitic series resistances

1/ < e1 > f < /e1 > noise experiments were performed for n-p-n GaAs/AlGaAs HBTs as a function of forward bias at room temperature. The experimental data are discussed with the help of new expressions for the 1/ < e1 > f < /e1 > noise in bipolar transistors where the influence of internal parasitic series resistances has been taken into account. At low forward currents the 1/ < e1 > f < /e1 > noise is determined by spontaneous fluctuations in the base and collector currents. At fixed bias, the collector current noise exceeds the base current noise. At higher forward currents the parasitic series resistances and their 1/ < e1 > f < /e1 > noise become important. Experimental results from the literature are compared with the results