DETERMINATION OF THE TRAP ENERGY-LEVELS AND THE EMITTER AREA DEPENDENCE OF NOISE IN POLYEMITTER BIPOLAR JUNCTION TRANSISTORS FROM GENERATION RECOMBINATION NOISE SPECTRA

A noise model for bipolar junction transistors based on generation-recombination (GR) noise originating from the traps located in the space-charge region of the emitter-base junction is derived. The model indicates that the current noise power owing to traps located inside the base-emitter depletion region should be proportional to the square of the collector current and inversely proportional to the emitter area. In addition, the model shows how the activation energy of a trap and the quasi-Fermi level can be related to the rising and falling edges of a GR noise spectrum by plotting the noise power against the reciprocal absolute temperature. Predictions from the noise model were compared with experimental data using seven bipolar transistors with emitter areas varying from 1.6 to 144 mum2. The noise measurements were performed at 10 temperatures between 10 and 100-degrees-C and at different biasing currents. From the measurements. the base current noise power spectra (S(ib)) is found to be proportional to the square of the base current (i(b)) and inversely proportional to the square of the emitter area. By plotting the noise power against the reciprocal temperature on a log-log graph and performing a linear least square fit on part of the data, a trap energy level of 821 meV above the valence band was determined.