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- von Haartman, Martin, et al.
(författare)
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Random telegraph signal noise in SiGe heterojunction bipolar transistors
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:8, s. 4414-4421
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Tidskriftsartikel (refereegranskat)abstract
- In this work, random telegraph signal (RTS) noise in SiGe heterojunction bipolar transistors (HBTs) was characterized both as a function of bias voltage and temperature. The RTS amplitudes were found to scale with the total base current, and the characteristic times in the higher and lower RTS state were found to decrease rapidly with bias voltage, approximately as 1/exp(qV(BE)/kT) or stronger. The RTS amplitudes were explained by a model based on voltage barrier height fluctuations across the base-emitter junction induced by trapped carriers in the space charge region. It was shown that the relative RTS amplitudes DeltaI(B)/I-B decrease exponentially with temperature in this model, which also was verified by measurements. The trapping/detrapping mechanism was suggested to be electron and hole capture, where the hole capture process occurs by tunneling. The characteristic times in both the lower and higher RTS state were in some cases found to decrease exponentially with temperature, characteristic for a thermally activated process, and in some cases found to be only weakly temperature dependent. The former behavior was explained by a multiphonon process with thermally activated capture cross sections, and an activation energy of 0.39 eV was extracted. RTS amplitudes proportional to the nonideal base current component or weaker were also found, originating from traps at the Si/SiO2 interface at the emitter periphery. The trapped carriers affect the recombination rate in the base-emitter space charge region, probably by changing the number of carriers. In this case, DeltaI(B)/I-B only showed a weak temperature dependence, which correlates well with this model. Characteristic times that decreased exponentially with temperature were observed, originating from a multiphonon process in the SiO2 with an activation energy for the capture cross section of 0.29 eV.
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